Question 1

In a typical oxidation reaction as defined in redox chemistry, what happens to the electrons of the species that is being oxidised?

Accepted Answer

Introduction / Context: Oxidation and reduction are key ideas in both chemistry and biology. They occur in reactions ranging from corrosion and combustion to cellular respiration and industrial processes. Modern definitions of oxidation and reduction are based on electron transfer. This question asks what happens to the electrons of the species that is undergoing oxidation in a redox reaction. Given Data / Assumptions: A redox reaction involves two half reactions, one oxidation and one reduction. Oxidation and reduction can be defined in several ways, including in terms of electron transfer. We use the modern electron based definition here. Protons and neutrons reside in the nucleus and usually do not change in ordinary redox reactions. Concept / Approach: In the electron transfer view, oxidation is defined as the loss of electrons by a species, and reduction is defined as the gain of electrons by a species. You can remember this using the phrase OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons). When a metal atom forms a positive ion, it has been oxidised because it gives up electrons. When a non metal or an ion gains electrons, it has been reduced. Protons and neutrons are largely unchanged in typical chemical reactions, which involve only the electron clouds around atoms. Step-by-Step Solution: Step 1: Recall the OIL RIG memory aid: Oxidation is loss, reduction is gain of electrons. Step 2: Identify that the question asks specifically about oxidation, not reduction. Step 3: Therefore, the species that is oxidised must be losing electrons during the reaction. Step 4: Check that no mention is made of changes in protons or neutrons in the usual definition of chemical oxidation. Step 5: Choose the option stating that electrons are lost from the species undergoing oxidation. Verification / Alternative check: Consider the reaction of sodium with chlorine: 2Na + Cl2 → 2NaCl. In terms of ions, sodium goes from neutral Na to Na+ by giving up one electron per atom, while chlorine goes from Cl2 to chloride ions Cl− by gaining electrons. Here sodium is oxidised because it loses electrons, and chlorine is reduced because it gains electrons. Many other examples, such as the formation of magnesium oxide from magnesium and oxygen, reinforce the same pattern. None of these reactions involve loss of protons or neutrons from the nucleus, which remain constant in chemical changes. Why Other Options Are Wrong: - Protons are lost from the nucleus: This would change the element itself and is associated with nuclear reactions, not standard chemical oxidation. - Neutrons are lost from the nucleus: Again, this describes nuclear processes, not typical oxidation in chemical reactions. - Electrons are gained by the species: Gaining electrons defines reduction, not oxidation. - Protons are gained by the species: There is no standard definition of oxidation based on gaining protons in basic chemistry; proton transfer is used in acid base reactions, not in defining redox changes. Common Pitfalls: Some students remember older definitions of oxidation such as addition of oxygen or removal of hydrogen and forget that these are special cases, not the most general rule. Others misapply the OIL RIG mnemonic and confuse which process involves loss or gain. Always focus on electrons: oxidation is electron loss, reduction is electron gain. This rule works for all redox reactions and avoids confusion when oxygen or hydrogen is not involved. Final Answer: In an oxidation reaction, the oxidised species Electrons are lost from the species.

Question 2

In the composition of stainless steel, which element primarily contributes to increasing the hardness and strength of the alloy?

Accepted Answer

Introduction / Context: Stainless steel is an important alloy used in cutlery, construction, machinery, and many household items. Its properties, such as hardness, strength, and resistance to corrosion, depend on the elements added to iron. This question asks which element specifically gives hardness and additional strength to stainless steel, a point often highlighted in discussions of steel alloys and material science. Given Data / Assumptions: Stainless steel is an alloy based on iron. Carbon is a key hardening element in steels. Other elements such as chromium, nickel, and sometimes molybdenum are also added to improve corrosion resistance and other properties, but are not listed here. The options include zinc, carbon, lead, tin, and gold. Concept / Approach: Plain carbon steel and alloy steels derive much of their hardness and tensile strength from the presence of carbon atoms in the iron lattice. Carbon atoms occupy interstitial positions between iron atoms, making it more difficult for the crystal structure to deform, which increases hardness and strength. Stainless steels are steels that contain chromium (and often nickel) for corrosion resistance, but they still rely on carbon to achieve desired hardness levels, especially in martensitic grades. Zinc, lead, tin, and gold do not play this specific role in stainless steels. Step-by-Step Solution: Step 1: Recall that steel is essentially an alloy of iron and carbon, and that varying carbon content controls hardness and strength. Step 2: Understand that stainless steel builds on this concept by adding chromium and other elements, but carbon remains important for hardness. Step 3: Examine the options and identify carbon as the only element commonly recognised as a hardening element in steels. Step 4: Recognise that zinc, lead, tin, and gold are not part of the standard stainless steel composition for hardness; lead and tin are soft metals, and gold is soft and expensive. Step 5: Conclude that carbon is the correct element that gives hardness to stainless steel. Verification / Alternative check: Materials science references describe how carbon content in steel affects the formation of different microstructures such as pearlite, bainite, and martensite. Higher carbon content generally allows for higher hardness and strength after appropriate heat treatment. Stainless steels are often classified as austenitic, ferritic, or martensitic, with martensitic stainless steels containing enough carbon to be hardened by heat treatment. None of the other listed elements have this primary role in hardness under the usual composition of stainless steel, confirming that carbon is the key hardening element mentioned in school chemistry. Why Other Options Are Wrong: - Zinc: Often used for galvanising iron to prevent rust, but not a typical alloying element that primarily controls hardness in stainless steel. - Lead: A very soft metal, sometimes added in small amounts to improve machinability, but it reduces strength rather than increasing hardness. - Tin: Sometimes used as a minor alloying element in certain bronzes and solders but does not define the hardness of stainless steels. - Gold: A soft, precious metal that is not part of stainless steel composition and is not used to adjust its hardness. Common Pitfalls: Students may remember that chromium and nickel are essential for corrosion resistance in stainless steel and be tempted to answer with one of them if they appear in an options list. In this particular question, those elements are not listed, so it is important to recall the more general fact that carbon content in any steel alloy, including stainless, strongly influences hardness and strength. Connecting the phrase high carbon steel with hardness can serve as a useful reminder. Final Answer: The element that primarily gives hardness to stainless steel is Carbon.

Question 3

Among the following sulphate salts, which one is practically insoluble in water under ordinary conditions?

Accepted Answer

Introduction / Context: Solubility rules for ionic compounds in water are an important part of school chemistry because they help predict whether precipitates will form in double displacement reactions. Many sulphate salts are soluble, but certain heavy metal sulphates are sparingly soluble or insoluble. This question asks you to identify which sulphate among the options is not soluble in water, that is, forms a precipitate rather than dissolving appreciably. Given Data / Assumptions: The options list sulphates of lead, zinc, potassium, sodium, and ammonium. General solubility rules for sulphate salts apply. We interpret not soluble as practically insoluble for exam purposes. Concept / Approach: General solubility rules state that most sulphate salts are soluble in water, with important exceptions such as sulphates of lead, barium, and calcium (which is moderately soluble). Alkali metal sulphates (like sodium and potassium sulphates) and ammonium sulphate are soluble. Zinc sulphate is also soluble in water. Lead sulphate, however, is considered insoluble or only very sparingly soluble, which means it forms a solid precipitate in water and in reactions producing PbSO4. Therefore, among the given choices, lead sulphate is the one that is not soluble in water. Step-by-Step Solution: Step 1: Recall the solubility rule that most sulphates are soluble except those of lead, barium, and partly calcium. Step 2: Identify the sulphates of alkali metals (sodium and potassium) and ammonium as definitely soluble in water. Step 3: Recognise that zinc sulphate is a typical metal sulphate that dissolves in water to give Zn2+ and SO4^2- ions. Step 4: Note that lead sulphate, PbSO4, is specifically mentioned in solubility tables as insoluble or sparingly soluble. Step 5: Conclude that lead sulphate is the sulphate that is not soluble in water among the options. Verification / Alternative check: Laboratory observations confirm that when solutions containing lead ions and sulphate ions are mixed, a white precipitate of lead sulphate forms and does not dissolve readily. In contrast, compounds like sodium sulphate and potassium sulphate dissolve easily to make clear solutions. Commercial fertilisers such as ammonium sulphate are also water soluble and used to supply nutrients to plants. Solubility tables summarise that PbSO4 is one of the important insoluble sulphates, while ZnSO4, Na2SO4, K2SO4, and (NH4)2SO4 are all soluble. These independent checks validate the conclusion. Why Other Options Are Wrong: - Zinc sulphate: ZnSO4 is soluble in water and is often used in solutions for agricultural and laboratory purposes. - Potassium sulphate: As an alkali metal sulphate, K2SO4 is soluble in water and used as a soluble potash fertiliser. - Sodium sulphate: Na2SO4 is also an alkali metal sulphate and is soluble in water, used in detergents and industry. - Ammonium sulphate: (NH4)2SO4 is a soluble fertiliser salt and dissolves easily in water. Common Pitfalls: Students sometimes remember that some sulphates are insoluble but mix up which metal ions are involved, confusing lead sulphate with zinc sulphate or others. Another mistake is to assume that all sulphates behave in the same way. To avoid confusion, remember the pattern that most sulphates are soluble, but lead sulphate and barium sulphate are classic insoluble examples, with calcium sulphate having limited solubility. Linking these exceptions clearly with the corresponding metals helps when quickly analysing precipitation reactions in exam questions. Final Answer: The sulphate that is not soluble in water is Lead sulphate.

Question 4

In basic general chemistry and metallurgy, haematite is an important ore or mineral that is used as a major source of which metal for industrial extraction?

Accepted Answer

Introduction / Context: This general chemistry question tests your knowledge of common metallic ores and the metals that are extracted from them. In competitive examinations, questions about matching minerals or ores with the corresponding metal are very frequent because they connect basic chemistry with practical metallurgy. Haematite is a very important iron bearing ore that has supported the iron and steel industry for decades, so recognizing it is essential for anyone studying basic science, engineering, or general knowledge. By identifying the metal associated with haematite, you also strengthen your understanding of how raw materials move from the earth into industrial production lines and ultimately into bridges, buildings, vehicles, and machinery. Given Data / Assumptions: - The ore mentioned in the question is haematite. - You are asked to identify which metal is primarily obtained from this ore. - Options include zinc, iron, lead, and manganese, all of which are common industrial metals. - Only one of these metals is correctly linked to haematite as its chief ore. Concept / Approach: To solve this question, you must recall the standard list of important ores and their corresponding metals. Haematite is a reddish brown iron oxide ore with the approximate formula Fe2O3. It is one of the most important ores of iron and is widely mined all over the world. Other metals listed in the options, such as zinc, lead, and manganese, also have characteristic ores, but those ores have different names like sphalerite, galena, and pyrolusite. Therefore, the approach here is to match haematite with iron based on commonly taught ore metal pairs in basic chemistry and metallurgy. Step-by-Step Solution: Step 1: Recall that ores are naturally occurring minerals from which metals can be extracted economically. Step 2: Remember that haematite is a well known iron ore with a high percentage of iron content. Step 3: Note that haematite has a typical formula close to Fe2O3 and occurs as a reddish brown mineral. Step 4: Compare each option and pair metals with their standard ores: zinc with sphalerite, lead with galena, manganese with pyrolusite, and iron with haematite. Step 5: Conclude that the metal obtained from haematite is iron, making Iron the correct answer. Verification / Alternative check: A quick way to verify your answer is to review a standard table of important ores and their metals from a school level chemistry book. Haematite is always listed under iron ores along with magnetite and siderite. You can also recall that iron and steel plants often mention haematite as their principal raw material. No standard reference ever lists haematite as an ore of zinc, lead, or manganese, confirming that the link with iron is correct. Therefore, cross checking with well known ore lists strongly supports the selection of iron as the correct metal for haematite. Why Other Options Are Wrong: Zinc is mainly obtained from ores such as sphalerite or zinc blende, not from haematite. Lead is primarily extracted from the ore galena, which is lead sulphide. Manganese is commonly obtained from ores such as pyrolusite and rhodochrosite rather than haematite. Hence, zinc, lead, and manganese do not match the ore haematite and are therefore incorrect choices in this question. Common Pitfalls: A common mistake is to confuse haematite with other metal oxides simply because many ores are oxides or sulphides. Students may also mix up haematite with bauxite or magnetite due to similar sounding names. Another pitfall is guessing randomly among different metals without systematically recalling the correct ore metal pairs. To avoid such errors, it is helpful to memorize a short list of common ores for each major metal and revise it regularly before examinations. Final Answer: The metal that is obtained from the ore haematite is Iron.

Question 5

In basic inorganic chemistry, what is the correct chemical formula of aluminium nitride, the binary compound formed between aluminium and nitrogen?

Accepted Answer

Introduction / Context: This question tests your understanding of writing chemical formulas for binary ionic compounds, specifically aluminium nitride. In many entrance and board examinations, candidates are expected to translate a compound name into its correct empirical formula by using valency rules and charge balance. Aluminium nitride is an important ceramic material and a classic example used in textbooks to illustrate the bonding between a metal cation and a nonmetal anion. Knowing its correct formula strengthens your grasp of ionic compounds, oxidation states, and the systematic way in which formulas are derived from element symbols and charges. Given Data / Assumptions: - The compound name given is aluminium nitride. - Aluminium is a metal belonging to group 13 of the periodic table. - Nitrogen is a nonmetal from group 15 and forms nitride ions in ionic compounds. - You must select the correct chemical formula from four closely related options. Concept / Approach: The main concept here is charge balance in ionic compounds. Aluminium usually forms Al3+ ions, while nitrogen forms nitride ions, written as N3 minus. In a stable ionic compound, the total positive charge must balance the total negative charge so that the overall compound is electrically neutral. Once you know the common charges on aluminium and nitrogen, you can combine the ions in the simplest whole number ratio that produces a neutral compound. The formula is written by placing the metal symbol first followed by the nonmetal symbol, with subscripts indicating the number of each ion required for neutrality. Step-by-Step Solution: Step 1: Identify the cation and anion involved. Aluminium forms Al3 plus ions and nitrogen forms N3 minus ions called nitride. Step 2: Apply the neutralization rule for ionic compounds. The algebraic sum of all ionic charges must equal zero in the final formula. Step 3: Observe that one Al3 plus ion and one N3 minus ion already balance each other because 3 plus and 3 minus add to zero. Step 4: Since a one to one ratio of aluminium to nitrogen gives a neutral compound, there is no need for any additional subscripts. Step 5: Write the formula with the metal first and nonmetal second, giving AlN as the correct chemical formula for aluminium nitride. Verification / Alternative check: As a quick alternative check, you can use the criss cross method that many students use to write ionic formulas. Take the valency or charge magnitude of aluminium, which is 3, and of nitride, which is also 3. Criss cross the numbers as subscripts to get Al3N3 and then reduce the subscripts to the simplest whole number ratio by dividing both by 3. This simplification gives AlN. Standard chemistry reference tables and textbooks also list aluminium nitride with the formula AlN, confirming that this choice is correct and consistent with practice. Why Other Options Are Wrong: Al2N would imply a total positive charge of 2 multiplied by 3 plus, which is 6 plus, on aluminium and a total negative charge of 3 minus on nitrogen, giving an overall 3 plus charge, so it is not neutral. AlN2 would correspond to 3 plus from aluminium and 2 multiplied by 3 minus which is 6 minus from nitrogen, leading to a net negative charge. AlN3 is even more unbalanced. None of these formulas satisfies charge neutrality, so they are not acceptable empirical formulas for aluminium nitride. Common Pitfalls: Students often forget to consider the magnitude of ionic charges and instead write formulas by guesswork or by simply matching subscripts to group numbers. Another common mistake is not simplifying larger subscripts like Al3N3 down to the lowest ratio. Some learners may also confuse nitrides with nitrates and mistakenly think aluminium nitride should contain oxygen, which is incorrect. Always remember to identify the ionic charges clearly, enforce overall charge neutrality, and then reduce the subscripts to the simplest whole number ratio. Final Answer: The correct empirical chemical formula of aluminium nitride is AlN.

Question 6

In the context of nuclear materials and strategic minerals, uraninite is an important ore or mineral of which element?

Accepted Answer

Introduction / Context: This question belongs to the general knowledge section of chemistry and earth science, focusing on the identification of important ores and their corresponding elements. Uraninite is a well known radioactive mineral that plays a major role in the nuclear energy industry because it contains high concentrations of uranium. Examinations frequently test awareness of such key ores, since they link geology, energy resources, and environmental issues. By correctly associating uraninite with uranium, you show that you understand the basic raw materials behind nuclear reactors, nuclear fuel cycles, and some strategic defense applications. Given Data / Assumptions: - The name of the ore or mineral given is uraninite. - You are asked which element this ore primarily provides. - Options include zinc, uranium, titanium, and aluminium, all of which are industrially important metals. - Only one of these metals is correctly associated with uraninite in standard reference tables. Concept / Approach: The approach is based on remembering standard ore element pairs. Uraninite, sometimes also referred to as pitchblende, is a uranium oxide mineral that is rich in uranium content. Recognizing its association with uranium is critical for questions related to nuclear chemistry and radioactive minerals. The other listed metals, such as zinc, titanium, and aluminium, are derived from completely different ores like sphalerite, ilmenite or rutile, and bauxite. Therefore, the task is to identify which option naturally matches the root word present in uraninite and to confirm that this match is consistent with basic chemistry and geology sources. Step-by-Step Solution: Step 1: Note the name of the ore, uraninite, and observe that it contains the word part uran, which hints at uranium. Step 2: Recall that uraninite is a uranium oxide mineral with high uranium content, often approximated as UO2 with additional oxidized forms. Step 3: Review the options and recognize that uranium is a heavy radioactive metal used as fuel in nuclear reactors. Step 4: Compare this with other metals such as zinc, titanium, and aluminium, which are mined from entirely different ores. Step 5: Conclude that uraninite is an ore of uranium, making Uranium the correct answer. Verification / Alternative check: You can verify this by consulting any standard textbook or reliable online source about radioactive minerals. Uraninite is consistently described as the chief ore of uranium and is recognized for its importance in uranium mining. Additionally, nuclear power related discussions often mention that uranium ore deposits contain minerals such as uraninite or pitchblende. No credible source lists uraninite as an ore of zinc, titanium, or aluminium, which further confirms that uranium is the only accurate match. Therefore, cross checking with reference data supports the correctness of the answer. Why Other Options Are Wrong: Zinc is commonly obtained from ores like sphalerite or zinc blende. Titanium comes mainly from mineral sources such as ilmenite and rutile. Aluminium is produced primarily from bauxite ore. None of these metals use uraninite as their main ore. Hence, the options zinc, titanium, and aluminium do not correctly match uraninite and must be rejected as incorrect answers in this context. Common Pitfalls: A typical error is to ignore the word root and choose randomly from the list of metals. Some students may also confuse uraninite with other oxide minerals, associating it incorrectly with more familiar metals like aluminium. Another pitfall is not paying attention to radioactive minerals in the syllabus and therefore missing this simple but important connection. To avoid such mistakes, it is helpful to learn a small set of key ores for strategic elements such as uranium, iron, aluminium, and copper and to relate ore names to element names wherever possible. Final Answer: Uraninite is an important ore or mineral of Uranium.

Question 7

In atmospheric chemistry and geophysics, the upper part of the heterosphere is composed almost completely of which gas?

Accepted Answer

Introduction / Context: This question examines your understanding of the structure and composition of the Earth atmosphere, particularly the region known as the heterosphere. In school level geography and environmental science, the atmosphere is often divided into layers based on temperature, composition, and mixing characteristics. At higher altitudes, gas molecules become separated according to their molecular mass, forming the heterosphere. Knowing which gas dominates the upper heterosphere helps you understand how light gases behave in the gravitational field of the planet and why certain space based measurements detect specific gases at very high altitudes. Given Data / Assumptions: - The question focuses on the upper part of the heterosphere in the atmosphere. - You must identify which gas is present almost exclusively in that upper region. - The options are ozone, nitrogen, oxygen, and hydrogen, which are all known atmospheric gases. - It is assumed that you are familiar with the basic idea that lighter gases can rise higher in the atmosphere. Concept / Approach: The key concept is that the atmosphere can be divided into the homosphere, where gases are well mixed, and the heterosphere, where gases are stratified by molecular weight. In the lower layers of the atmosphere, nitrogen and oxygen are dominant and almost uniformly mixed. However, in the heterosphere at very high altitudes, heavier gases remain closer to the lower boundary, while lighter gases gradually dominate as you move upward. Since hydrogen is the lightest of the gases listed, it tends to be found in the uppermost parts of the atmosphere. The task is to link the idea of molecular mass and gravitational separation with the composition of the upper heterosphere. Step-by-Step Solution: Step 1: Recall that the lower atmosphere, known as the homosphere, has a fairly uniform composition dominated by nitrogen and oxygen. Step 2: Understand that the heterosphere lies above the homosphere and extends into regions where gases separate based on density and molecular mass. Step 3: Recognize that in the lower heterosphere, heavier gases like nitrogen and oxygen may still be present, but as altitude increases, lighter gases become more common. Step 4: Identify hydrogen as the lightest gas among the options given, significantly lighter than ozone, nitrogen, or oxygen. Step 5: Conclude that at the upper part of the heterosphere, hydrogen becomes the predominant gas, so Hydrogen is the correct answer. Verification / Alternative check: You can verify this by consulting diagrams of atmospheric composition in standard geography or environmental science textbooks. These diagrams often show layers such as the troposphere, stratosphere, mesosphere, and thermosphere, alongside the distinction between homosphere and heterosphere. In the very high altitude exosphere, which lies beyond the upper heterosphere, hydrogen and helium form the bulk of the gas content. Since the question specifically asks about the upper heterosphere, which transitions toward this region, the dominance of hydrogen is consistent and widely accepted in atmospheric science literature. Why Other Options Are Wrong: Ozone is concentrated mainly in the ozone layer within the stratosphere and does not dominate the extreme upper atmosphere. Nitrogen is the most abundant gas in the lower atmosphere but does not remain the principal gas at the highest altitudes because it is heavier than hydrogen and helium. Oxygen is also abundant in the lower and middle atmosphere, but its proportion falls off in the upper heterosphere. Hence, ozone, nitrogen, and oxygen do not match the description of the gas that almost completely composes the upper heterosphere. Common Pitfalls: A common mistake is to mechanically choose nitrogen because it is the most abundant gas in the atmosphere overall, without considering how composition changes with altitude. Another pitfall is to think of ozone whenever high altitude atmospheric chemistry is mentioned, even though ozone is concentrated much lower. Students may also overlook the role of molecular mass in gravitational separation of gases. To avoid these errors, always relate the concept of layers to the physical properties of gases and remember that lighter gases can dominate at extreme heights above the Earth surface. Final Answer: The upper part of the heterosphere is composed almost completely of Hydrogen.

Question 8

In environmental chemistry, methane is an air pollutant that is significantly produced by which of the following processes?

Accepted Answer

Introduction / Context: This question tests your knowledge of environmental chemistry and sources of greenhouse gases, especially methane. Methane is a potent greenhouse gas that contributes significantly to global warming and climate change even though its concentration in the atmosphere is lower than carbon dioxide. Understanding the major natural and human related sources of methane is important in climate science, agriculture, and environmental policy. Examinations often include questions that ask you to identify which industrial or biological processes emit key pollutants, so recognizing that animal digestion is a major methane source is highly relevant. Given Data / Assumptions: - The pollutant of interest is methane gas in the atmosphere. - Several possible processes are listed, including ultraviolet action on nitrogen compounds, fertilizer manufacture, incomplete coal combustion, and digestion of food by animals. - You are expected to identify the dominant methane producing process among the options given. - The focus is on typical textbook level sources, not rare or highly specialized reactions. Concept / Approach: The core concept is that methane is produced by anaerobic decomposition of organic matter, especially in the digestive systems of ruminant animals such as cattle, sheep, and goats. Microorganisms in the stomachs of these animals break down plant material and generate methane as a by product, which then escapes through belching and other processes. While methane can also originate from wetlands, landfills, and some industrial activities, the most prominent and widely taught source in basic environmental science is enteric fermentation in animals. Therefore, you must connect the idea of animal digestion with methane generation and distinguish it from processes that mainly produce other pollutants such as nitrogen oxides or carbon monoxide. Step-by-Step Solution: Step 1: Recall that methane, CH4, is a colorless, odorless gas that acts as a strong greenhouse gas in the atmosphere. Step 2: Remember that one of the largest natural and agricultural sources of methane is microbial activity in the digestive systems of ruminant animals, a process called enteric fermentation. Step 3: Examine each option and match it with its typical emissions. Ultraviolet action on nitrogenous compounds is more closely associated with photochemical smog and nitrogen oxides. Step 4: Manufacturing ammoniacal fertilizers and burning coal in insufficient air are processes more commonly associated with emissions of oxides of nitrogen, carbon monoxide, and other gases, not primarily methane. Step 5: Conclude that digestion of food by animals, especially ruminant livestock, is the main methane producing process in the given list, so that option is correct. Verification / Alternative check: To verify this reasoning, you can refer to climate change reports or educational summaries that list the main anthropogenic sources of methane. These sources consistently emphasize agriculture and livestock, particularly ruminants, as major contributors to methane emissions. Wetlands and rice paddies are also listed, but those are not among the options here. Industrial processes like fertilizer manufacturing may involve ammonia and nitrogen compounds, but they are not highlighted as dominant methane emitters. Therefore, cross checking with reliable environmental data supports the conclusion that animal digestion is the correct answer. Why Other Options Are Wrong: The action of ultraviolet light on nitrogenous compounds leads mainly to the formation of nitrogen oxides and contributes to photochemical smog, not primarily methane. The manufacture of ammoniacal fertilizers deals with ammonia and related nitrogen species rather than methane emission as a central issue. Burning coal in insufficient air generates carbon monoxide and soot particles but not large amounts of methane. While small amounts of methane may occur in some combustion processes, the textbook emphasis is on the greenhouse gas release from enteric fermentation in animals. Hence, these options do not represent the main methane source and are considered incorrect. Common Pitfalls: Students often assume that any industrial process, such as fertilizer production or coal burning, must be the correct answer because these are obviously polluting activities. This leads them to overlook biological sources like animal digestion, which also play a huge role in greenhouse gas emissions. Another common mistake is not distinguishing between different pollutants and simply guessing based on which option sounds most technical. To avoid such errors, it is important to connect each process with its primary pollutants and to remember that agriculture and livestock contribute significantly to methane in the atmosphere. Final Answer: Methane as an air pollutant is significantly produced by digestion of food by animals.

Question 9

In basic atomic chemistry of hydrogen and its isotopes, which of the following statements is false?

Accepted Answer

Introduction / Context: This question focuses on isotopes of hydrogen, which is one of the most fundamental topics in basic chemistry and nuclear science. Hydrogen has three main isotopes, namely protium, deuterium, and tritium, each with the same number of protons but different numbers of neutrons and therefore different masses. Competitive exams often test whether you remember the names, relative abundances, and simple properties of these isotopes. Here, you are asked to identify the one false statement among several correct statements about hydrogen isotopes. This requires accurate recall of which isotope is most abundant and what is meant by heavy hydrogen. Given Data / Assumptions: - The question presents four statements about hydrogen and its isotopes. - You must decide which statement is factually incorrect according to standard chemistry knowledge. - It is assumed that you know the basic composition and abundances of protium, deuterium, and tritium. - Only one statement is false; the others are true and consistent with scientific data. Concept / Approach: The core concept involves isotopes, which are atoms of the same element with the same number of protons but different numbers of neutrons. Hydrogen has three commonly discussed isotopes. Protium, written as hydrogen 1, has one proton and no neutrons and is by far the most abundant isotope in nature. Deuterium, hydrogen 2, has one proton and one neutron and is known as heavy hydrogen because it has roughly double the mass of protium. Tritium, hydrogen 3, has one proton and two neutrons and is radioactive. The approach is to check each given statement against these facts to see which one contradicts well established information. Step-by-Step Solution: Step 1: Recall that protium has one proton and zero neutrons and makes up the vast majority of natural hydrogen, well over 99 percent. Step 2: Remember that deuterium has one proton and one neutron, doubling its mass relative to protium and earning the name heavy hydrogen. Step 3: Note that tritium has one proton and two neutrons, which means its mass is approximately three times that of protium. Step 4: Compare the statements. Saying that a normal hydrogen atom is roughly a third of the mass of tritium is reasonable because tritium has about triple the mass of protium. Step 5: Confirm that deuterium being called heavy hydrogen and having one neutron are both correct statements. Step 6: Evaluate the statement that protium is the rarest isotope. This is clearly false because protium is actually the most abundant isotope of hydrogen in the universe. Step 7: Therefore, identify the false statement as the one that claims protium is the rarest isotope of hydrogen. Verification / Alternative check: You can verify these facts by checking a standard chemistry textbook or periodic table reference. These sources will state that protium is the dominant form of hydrogen, deuterium is present in very small amounts, and tritium is extremely rare and radioactive. They will also mention that deuterium is known as heavy hydrogen and has one neutron. Simple mass comparisons also support the idea that protium has roughly one third the mass of tritium. Therefore, any claim that protium is the rarest isotope contradicts well established data and must be considered false. Why Other Options Are Wrong: The statement that hydrogen atom is roughly a third of the mass of tritium is essentially correct because tritium contains two additional neutrons compared to protium, making its mass about three times larger. Deuterium is indeed called heavy hydrogen because it weighs more than protium due to the presence of one neutron. The statement that deuterium atom has one neutron is also accurate. None of these statements conflict with standard isotope descriptions, so they are not false and therefore not the desired answer. Common Pitfalls: A common mistake is to mix up abundance with mass. Some students think that the heavier isotopes must be more important or more common, which can lead them to accept the idea that protium is rare. Others may vaguely remember that heavy hydrogen is unusual and mistakenly apply that label to the wrong isotope. Confusion between names and mass numbers is also frequent. To avoid such pitfalls, always link the names protium, deuterium, and tritium with their actual compositions and relative abundances. Remember clearly that protium dominates, deuterium is rare but stable, and tritium is very rare and radioactive. Final Answer: The false statement is that Protium is the rarest isotope of hydrogen.

Question 10

In soil science and plant nutrition, which of the following forms of nitrogen supplied to plants is most directly associated with the action of biofertilizers?

Accepted Answer

Introduction / Context: This question deals with the concept of biofertilizers in agriculture and the chemical forms of nitrogen that plants can readily absorb. Biofertilizers are living microorganisms, such as nitrogen fixing bacteria and cyanobacteria, that enhance nutrient availability in the soil without the environmental drawbacks of excessive chemical fertilizer use. One of their key functions is to convert atmospheric nitrogen or organic nitrogen into forms that plants can actually use, primarily nitrate or ammonium ions. Understanding which nitrogen form is directly linked with the activity of biofertilizers helps you connect microbiology, soil chemistry, and sustainable farming practices. Given Data / Assumptions: - The question mentions biofertilizers, which are biological agents rather than synthetic chemicals. - Four nitrogen related substances are listed as options: urea, ammonia, uric acid, and nitrates. - You are expected to identify the nitrogen form that is most directly associated with the action of biofertilizers and easily absorbed by plant roots. - It is assumed that you know that plants usually take up nitrogen as nitrate or ammonium ions from the soil solution. Concept / Approach: Biofertilizers like Rhizobium, Azotobacter, and blue green algae work by fixing atmospheric nitrogen into biologically available forms in the soil. They either directly produce ammonium that is further converted by nitrifying bacteria or facilitate processes that lead to increased nitrate availability. Plants predominantly absorb nitrogen as nitrate ions and also as ammonium ions. Among the options, nitrates represent the final oxidized, plant available form that results from microbial activity in the nitrogen cycle. Urea and uric acid are organic or synthetic compounds that need further microbial breakdown, and ammonia is a gaseous or ionic form that is intermediate in the cycle. Therefore, the best match with the phrase associated with the action of biofertilizers and plant uptake is nitrates. Step-by-Step Solution: Step 1: Recall that biofertilizers are living microorganisms that improve nutrient status by fixing nitrogen or solubilizing phosphates, rather than being direct chemical fertilizers. Step 2: Remember that plants typically absorb nitrogen from the soil in the form of nitrate ions, NO3 minus, and ammonium ions, NH4 plus. Step 3: Recognize that nitrogen fixing and nitrifying bacteria transform atmospheric nitrogen and organic nitrogen into ammonium and then nitrates, completing key steps in the nitrogen cycle. Step 4: Examine the options. Urea is a synthetic nitrogen fertilizer, uric acid is a nitrogenous waste product in animals, and ammonia is an intermediate that may be further converted. Step 5: Conclude that nitrates are the specific form strongly linked to microbial activity in soil and directly taken up by plants, so Nitrates is the correct answer. Verification / Alternative check: You can verify this by looking at diagrams of the nitrogen cycle in environmental science or biology textbooks. These diagrams typically show nitrogen fixing bacteria creating ammonium, which nitrifying bacteria convert into nitrites and then nitrates. Plant roots are shown absorbing mainly nitrate ions as their principal nitrogen source. Urea may be applied as a fertilizer, but it first must be hydrolyzed and further processed by soil microorganisms. Uric acid is not a standard fertilizer in crop fields. This confirms that nitrates are the most appropriate form associated with biofertilizer action and plant uptake. Why Other Options Are Wrong: Urea is a commonly used synthetic nitrogen fertilizer manufactured industrially; it is not itself a biofertilizer and must be converted to ammonium and then nitrates by microorganisms before plants can use it. Ammonia is an intermediate in the nitrogen cycle and can be used by plants in some forms, but it is not the main final product emphasized in discussions of biofertilizers and plant uptake. Uric acid is a nitrogenous waste compound excreted by birds and some animals, not a typical soil nitrogen source for crops. Therefore, these options do not directly capture the nitrogen form most clearly linked to biofertilizer activity in soils. Common Pitfalls: A frequent mistake is to select urea simply because it is a very familiar fertilizer name, without noticing that the question explicitly mentions biofertilizers, which are biological in nature. Some students may also choose ammonia because they know it contains nitrogen, but they forget that plants commonly take up nitrogen as nitrates in agricultural soils. Confusing the broader category of nitrogen fertilizers with the specific role and products of biofertilizers can also lead to errors. To avoid these pitfalls, always connect biofertilizers with microbial transformations of nitrogen and focus on the plant available forms highlighted in the nitrogen cycle. Final Answer: The nitrogen form most directly associated with the action of biofertilizers and readily taken up by plants is Nitrates.

Question 11

In biochemistry, which substance is a multibranched polysaccharide of glucose that serves as a major form of energy storage in animals and fungi?

Accepted Answer

Introduction / Context: This biochemistry question tests your understanding of important biological macromolecules, specifically polysaccharides that store or provide structural support. Living organisms use different glucose polymers for different purposes. Plants mainly store energy as starch and use cellulose for structure, whereas animals and fungi store energy as glycogen. Recognizing which polymer serves as the primary energy storage molecule in animals and fungi is essential for mastering carbohydrate metabolism and for interpreting textbook descriptions of liver and muscle energy reserves. Given Data / Assumptions: - The question refers to a multibranched polysaccharide made of glucose units. - The polysaccharide serves as a form of energy storage specifically in animals and fungi. - The options are glycogen, pectin, chitin, and cellulose, which are all polysaccharides found in nature. - Only one of these correctly matches all the clues given in the stem. Concept / Approach: The key concept centers on the classification of polysaccharides into storage and structural types. Glycogen is a highly branched glucose polymer stored mainly in the liver and muscles of animals and also present in fungi, where it acts as an energy reserve. Cellulose is a linear structural polysaccharide that reinforces plant cell walls. Pectin is a component of plant cell walls and is important in the middle lamella, contributing to fruit firmness and gelling. Chitin is a structural polysaccharide found in fungal cell walls and the exoskeletons of arthropods. Only glycogen matches the description of a multibranched glucose polysaccharide used widely for energy storage in animals and fungi. Step-by-Step Solution: Step 1: Focus on the words multibranched polysaccharide of glucose, which point toward a storage form rather than a purely structural one. Step 2: Recall that animals store excess glucose mainly in the form of glycogen in their liver and muscle tissues. Step 3: Remember that fungi also use glycogen as an energy storage molecule, paralleling the role of starch in plants. Step 4: Compare the other options. Pectin is a plant cell wall polysaccharide, chitin is structural in fungi and arthropods, and cellulose forms plant cell walls but is not a multibranched storage polysaccharide. Step 5: Conclude that glycogen is the only option that fits all parts of the definition, making Glycogen the correct answer. Verification / Alternative check: Verification can be done by consulting a biochemistry textbook or a standard biology reference that discusses carbohydrates. These resources consistently describe glycogen as a branched polymer of alpha glucose, analogous to the branched components of starch but with even more frequent branching. They also explicitly state that animals and fungi use glycogen as a primary storage form of glucose. Pectin, chitin, and cellulose are described as structural or gel forming components rather than the main rapid release energy stores in animals. This agreement across multiple sources confirms that glycogen is the correct choice. Why Other Options Are Wrong: Pectin is a complex polysaccharide present in plant cell walls and is important in fruit ripening and jam making, but it is not the main energy storage compound in animals or fungi. Chitin is a structural polysaccharide found in fungal cell walls and arthropod exoskeletons and is not primarily used for energy storage. Cellulose is a linear glucose polymer that strengthens plant cell walls and is not multibranched or used as a major energy reserve in animals or fungi. Therefore, these three polysaccharides do not fit the description in the question. Common Pitfalls: Students sometimes confuse glycogen with starch because both are glucose storage polymers. The clue about animals and fungi is important here, since starch is mainly a plant storage polysaccharide. Others may be tempted by cellulose because it is a very common polysaccharide, but they forget that it is linear and structural. Confusion between structural and storage functions of polysaccharides is a frequent source of mistakes. To avoid such errors, clearly associate glycogen with animal and fungal storage, starch with plant storage, and cellulose and chitin with structural roles. Final Answer: The multibranched glucose polysaccharide that stores energy in animals and fungi is Glycogen.

Question 12

In basic organic chemistry and everyday applications, which acid is used for making vinegar that is commonly used in kitchens and food preservation?

Accepted Answer

Introduction / Context: This question connects basic organic chemistry with everyday life by asking which acid is used in making vinegar. Vinegar is widely used in cooking, pickling, and food preservation and is one of the most familiar acidic substances in the kitchen. Understanding that vinegar is essentially a dilute solution of acetic acid helps you relate textbook knowledge about carboxylic acids to practical household examples. Examinations frequently ask such application based questions to test whether you can recognize the chemical names behind common products and distinguish between different organic acids. Given Data / Assumptions: - The product in question is vinegar, used in kitchens for flavoring and preservation. - You must identify which acid is responsible for the sour taste and properties of vinegar. - Four organic acids are listed: tartaric acid, malic acid, oxalic acid, and acetic acid. - Only one of these acids corresponds to the main component of vinegar. Concept / Approach: The key concept is that vinegar is a dilute aqueous solution of acetic acid, often around four to eight percent by volume. Acetic acid is a simple carboxylic acid with the formula CH3COOH. While other acids like tartaric, malic, and oxalic acid are found in fruits and plants and may contribute to sourness, they are not the principal acids used to produce standard culinary vinegar. By recalling the match between acetic acid and vinegar, you can easily answer this question. The approach is to connect the common everyday term vinegar with its underlying chemical composition in the language of organic chemistry. Step-by-Step Solution: Step 1: Recall from chemistry and general knowledge that vinegar is mainly an aqueous solution of acetic acid. Step 2: Remember that acetic acid is a carboxylic acid with the characteristic group COOH attached to a methyl group. Step 3: Compare the options. Tartaric acid is found in grapes and tamarind, malic acid in apples, and oxalic acid in spinach and some leafy vegetables. Step 4: None of these other acids is commonly used as the primary acid for commercial vinegar production. Step 5: Conclude that acetic acid is used for making vinegar, so Acetic acid is the correct answer. Verification / Alternative check: Verification is straightforward. Any reliable chemistry text or food science reference will describe vinegar as a dilute solution of acetic acid, with water as the solvent. The sharp smell and sour taste associated with vinegar are characteristic of acetic acid. Labels on vinegar bottles may even mention acetic acid content as a percentage. Meanwhile, tartaric, malic, and oxalic acids are discussed in the context of specific fruits and vegetables rather than as the direct basis of vinegar. This consistent description across multiple sources confirms that acetic acid is the correct choice. Why Other Options Are Wrong: Tartaric acid occurs naturally in grapes and is used in baking powder and some food products but does not define vinegar. Malic acid is abundant in apples and contributes to their sour taste but again is not the key component of vinegar. Oxalic acid is found in spinach and some leafy vegetables and is actually toxic in larger amounts, so it is not used as a kitchen vinegar acid. Therefore, although these acids are real and important in food chemistry, none of them is the main acid responsible for making vinegar. Common Pitfalls: Students may confuse the different fruit acids because tartaric and malic acids are commonly mentioned in relation to sour fruits and jams. Another common error is to think that any sour tasting acid may be used for vinegar without recalling the specific chemical name. Some may ignore the clue that vinegar is a very simple and widely standardized product based on acetic acid. To avoid these pitfalls, remember the direct association: vinegar corresponds to acetic acid, while tartaric, malic, and oxalic acids are primarily associated with specific fruits or plants rather than standard kitchen vinegar. Final Answer: Vinegar used in everyday life is made using Acetic acid.

Question 13

In general chemistry and mineral resources, manganite is an ore or mineral of which metal?

Accepted Answer

Introduction / Context: This question assesses your knowledge of common ores and the metals that are extracted from them, a frequent topic in general chemistry and geology based competitive exams. Manganite is a mineral whose name strongly hints at its associated metal. Being able to link manganite with manganese helps you understand the origin of important industrial materials such as steel alloys and dry cell components. It also reinforces the idea that ore names often reflect the metallic element they contain, which can be a helpful memory aid during examinations. Given Data / Assumptions: - The ore or mineral mentioned is manganite. - You must choose which metal is primarily obtained from this ore. - The options are beryllium, chromium, manganese, and copper, all of which are significant industrial metals. - Only one of these metals correctly corresponds to manganite according to standard mineralogy references. Concept / Approach: The main concept is matching mineral names to their metal contents. Manganite is a manganese oxide hydroxide mineral, commonly described as MnO(OH). The inclusion of the root mangan in the name points toward manganese. In contrast, the metals beryllium, chromium, and copper are obtained from completely different ores with names such as beryl, chromite, and chalcopyrite. Therefore, the approach is to recognize the naming pattern and to recall that manganite is indeed listed among manganese ores along with pyrolusite and psilomelane in most chemistry and geology textbooks. Step-by-Step Solution: Step 1: Note that the mineral name manganite includes the fragment mangan, which strongly suggests a relation to manganese. Step 2: Recall that manganite is typically described as a manganese oxide hydroxide mineral used as a manganese ore. Step 3: Review the options. Beryllium comes from ores such as beryl, chromium from chromite, and copper from ores such as chalcopyrite and malachite. Step 4: Observe that none of these other metals have ore names closely resembling manganite or are listed with manganite as a principal source. Step 5: Conclude that manganite is an ore of manganese, so the correct answer is Manganese. Verification / Alternative check: Verification can be done by consulting a table of common ores and their metals in any general chemistry or earth science textbook. These tables specify that manganese is extracted from minerals such as pyrolusite, manganite, and other manganese oxides. You will not find manganite listed under beryllium, chromium, or copper. Field guides to minerals also classify manganite as a manganese bearing ore. This consistent classification across reference sources confirms that manganese is the metal associated with manganite. Why Other Options Are Wrong: Beryllium is typically obtained from the mineral beryl and other beryllium silicates, not from manganite. Chromium is extracted mainly from chromite, an iron chromium oxide mineral. Copper is produced from ores such as chalcopyrite, bornite, and malachite. None of these metals use manganite as a principal ore. Thus, beryllium, chromium, and copper are incorrect matches for manganite in the context of ore metal relationships. Common Pitfalls: A common mistake is to guess based purely on familiarity with the metals listed rather than paying attention to the clues in the mineral name. Some students may also confuse manganite with magnetite, an iron ore, due to the similarity of the names. To avoid such errors, take a moment to parse the name manganite and notice its clear connection with manganese, and revise a short list of important ores and their metals as part of your exam preparation. Final Answer: Manganite is an ore or mineral of Manganese.

Question 14

In everyday safety applications and basic chemistry, modern fire extinguishers commonly emit which gas to help put out fires?

Accepted Answer

Introduction / Context: This question tests your understanding of the basic chemistry behind fire extinguishers, which are essential safety devices in homes, offices, and laboratories. Fire extinguishers work by removing heat, cutting off oxygen, or interrupting the chemical reactions that sustain a fire. Among the different extinguishing agents used, carbon dioxide gas is very common, especially in extinguishers meant for electrical and certain flammable liquid fires. Recognizing that carbon dioxide is the gas released from many fire extinguishers helps you connect practical safety knowledge with chemical principles related to combustion. Given Data / Assumptions: - The device under discussion is a fire extinguisher used to control or put out fires. - You are asked which gas such extinguishers commonly emit. - Options include carbon monoxide, chlorine, carbon dioxide, and nitrogen. - It is assumed that you know basic facts about combustion and how gases can influence fire behavior. Concept / Approach: The concept is that combustion requires three elements often called the fire triangle: fuel, heat, and oxygen. Fire extinguishers aim to remove or disrupt one of these elements. Carbon dioxide is denser than air and does not support combustion. When released from a fire extinguisher, it displaces oxygen around the flame and cools the area, thereby helping to smother the fire. Carbon monoxide and chlorine are toxic gases and are not used as safe extinguishing agents in common fire extinguishers. Nitrogen is relatively inert but is not the standard gas used in domestic and office extinguishers. Therefore, the logical choice is carbon dioxide. Step-by-Step Solution: Step 1: Recall that fire extinguishers often contain pressurized carbon dioxide, which is released as a cold gas or snow like substance. Step 2: Remember that carbon dioxide does not support combustion and helps to displace oxygen in the surrounding air. Step 3: Understand that reducing the availability of oxygen near the flame starves the fire and leads to its suppression. Step 4: Examine the options and recognize that carbon monoxide is a poisonous gas produced by incomplete combustion, not a deliberately used extinguisher gas. Step 5: Note that chlorine is a highly reactive and toxic gas, and nitrogen, although inert, is not normally used in standard portable extinguishers for the public. Step 6: Conclude that carbon dioxide is the widely used gas in many fire extinguishers, so Carbon dioxide is the correct answer. Verification / Alternative check: You can verify this by simply reading the labels printed on common fire extinguishers in public places, which often state carbon dioxide or CO2 as the extinguishing agent. Educational materials on fire safety also categorize extinguishers by type, mentioning CO2 extinguishers specifically for electrical and flammable liquid fires. Textbooks on basic chemistry and safety also explain that carbon dioxide suppresses fire by displacing oxygen and cooling the burning material. These consistent references confirm that carbon dioxide is the gas released by many fire extinguishers. Why Other Options Are Wrong: Carbon monoxide is a dangerous gas produced as a pollutant during incomplete combustion and is not intentionally stored in fire extinguishers. Chlorine gas is corrosive and harmful to humans and would be unsuitable as a firefighting agent in general environments. Nitrogen is an inert gas but is not commonly used in standard portable fire extinguishers for household or office use; specialized systems may use inert gas mixtures, but the textbook emphasis is on carbon dioxide. Therefore, these gases are incorrect choices in the context of this question. Common Pitfalls: Some students may choose carbon monoxide simply because it is a well known gas related to fires, but they overlook its toxic nature and the fact that it is a by product rather than a safety tool. Others might think of nitrogen because it is inert and makes up most of the atmosphere, yet they forget that typical extinguishers do not rely on nitrogen as the main agent. Confusion may also arise when students do not carefully recall what they have seen printed on real fire extinguisher cylinders. To avoid such mistakes, always associate carbon dioxide with CO2 extinguishers and remember that safety equipment uses agents that are effective and reasonably safe when used properly. Final Answer: Modern fire extinguishers commonly emit Carbon dioxide gas to help put out fires.

Question 15

In basic atomic structure, the atomic number of an atom gives the number of which fundamental particle?

Accepted Answer

Introduction / Context: This question comes from the core topic of atomic structure in chemistry and physics. The atomic number is one of the most important properties of an element because it defines the identity of the element in the periodic table. Knowing exactly what the atomic number represents is essential for understanding electron configurations, isotopes, and chemical behavior. Examinations frequently check whether students can correctly associate atomic number with the appropriate subatomic particle among protons, electrons, and neutrons. Given Data / Assumptions: - The question asks what quantity the atomic number of an atom indicates. - You are given options in terms of electrons, protons, neutrons, and neutrons plus protons. - It is assumed you know the basic structure of atoms according to the modern atomic model. - The question is about a neutral isolated atom, but the definition of atomic number itself is independent of charge state. Concept / Approach: The atomic number of an element is defined as the number of protons present in the nucleus of an atom of that element. This number is the key to the element identity; for example, every atom with atomic number 6 is carbon because it has six protons. In a neutral atom, the number of electrons equals the number of protons, so atomic number also equals the number of electrons in that special case. However, if the atom becomes an ion, the number of electrons can change while the atomic number and the number of protons remain constant. Therefore, the most fundamental and correct association is between atomic number and the number of protons in the nucleus. Step-by-Step Solution: Step 1: Recall the definition of atomic number, usually denoted by Z, as the number of protons in the nucleus of an atom. Step 2: Understand that this number determines the chemical identity and the position of the element in the periodic table. Step 3: Note that in a neutral atom, the number of electrons equals the number of protons, but electrons can be lost or gained to form ions. Step 4: Recognize that neutrons are not counted in the atomic number; instead, they contribute along with protons to the mass number. Step 5: Conclude that the only subatomic particle directly counted by the atomic number is the proton, so Protons is the correct answer. Verification / Alternative check: You can verify this by consulting periodic table information, where each element is listed with an atomic number corresponding to its proton count. For example, hydrogen has atomic number 1, helium 2, and lithium 3, which correspond exactly to their proton numbers. Additionally, isotopes of an element share the same atomic number but have different numbers of neutrons, showing that atomic number cannot be tied to neutrons. Charged species like ions still retain the same atomic number because their proton count is unchanged, confirming that atomic number is fundamentally linked to protons. Why Other Options Are Wrong: Electrons match the atomic number only in neutral atoms. Once an atom loses or gains electrons to form cations or anions, the electron count no longer equals the atomic number, so atomic number cannot generally be defined as the number of electrons. Neutrons vary even among isotopes of the same element and thus do not define the element identity. The sum of neutrons and protons is called the mass number, not the atomic number. Therefore, these other options do not correctly describe what atomic number represents. Common Pitfalls: Students sometimes confuse atomic number with mass number and may mistakenly think that atomic number counts neutrons plus protons. Others may assume atomic number always equals electron number because they mostly deal with neutral atoms in early lessons. This becomes misleading when ions are introduced. To avoid these pitfalls, focus on the precise definition: atomic number equals the number of protons in the nucleus, and mass number equals the sum of protons and neutrons. Remember that electrons can change when an atom forms ions, but the atomic number remains constant for a given element. Final Answer: The atomic number of an atom gives the number of Protons in its nucleus.

Question 16

In common household chemistry, which of the following substances is the everyday name for dilute acetic acid used in cooking and food preservation?

Accepted Answer

Introduction / Context: This question builds a bridge between basic organic chemistry and everyday life by asking you to identify the common name for dilute acetic acid. In kitchens around the world, people frequently use a sour liquid called vinegar for cooking, pickling, and cleaning. Chemically, this liquid is nothing but acetic acid dissolved in water at a relatively low concentration. Understanding this link reinforces your ability to recognize the chemical nature of familiar household substances and helps you see how textbook concepts about acids appear in practical contexts. Given Data / Assumptions: - The chemical substance of interest is dilute acetic acid, an organic carboxylic acid solution. - You must identify which everyday material corresponds to this dilute acetic acid. Concept / Approach: The key concept is that vinegar is a dilute aqueous solution of acetic acid, usually containing about four to eight percent acetic acid by volume. The rest of the solution is water. Baking soda is sodium bicarbonate, a basic compound rather than an acid. Copper sulphate and magnesium oxide are inorganic salts and oxides used for other purposes and have very different properties from acetic acid. Therefore, by matching the chemical name acetic acid with the culinary and household product known as vinegar, you can easily determine the correct answer. Step-by-Step Solution: Step 1: Recall that vinegar is a sour liquid widely used for cooking, pickling, and cleaning, and that it is known chemically as dilute acetic acid. Step 2: Remember that acetic acid has the formula CH3COOH and belongs to the carboxylic acid family. Step 3: Compare the options. Baking soda is sodium bicarbonate, NaHCO3, and behaves as a mild base in water. Step 4: Note that copper sulphate, CuSO4, is a blue salt often used in laboratories and agriculture, and magnesium oxide is a basic oxide used in industrial and medicinal settings. Step 5: Conclude that none of these match dilute acetic acid except vinegar, which is the common name for that solution, so Vinegar is correct. Verification / Alternative check: You can verify this by reading labels on commercial vinegar bottles, which commonly specify acetic acid content as a percentage. Chemistry textbooks and food science references likewise define vinegar as a dilute solution of acetic acid in water. Meanwhile, descriptions of baking soda clearly identify it as sodium bicarbonate, and the formulae of copper sulphate and magnesium oxide confirm that they are not carboxylic acids. This consistent agreement between real world packaging and scientific literature confirms that vinegar is the everyday name for dilute acetic acid. Why Other Options Are Wrong: Baking soda is a basic salt, not an acid, and is used for baking and cleaning but does not correspond to acetic acid. Copper sulphate is a blue crystalline salt primarily used as a fungicide, algicide, or laboratory reagent and is not related to the culinary use of vinegar. Magnesium oxide is a white basic oxide used in refractory materials and some medicines. None of these substances are dilute acetic acid or share the same common usage as vinegar, so they are incorrect matches for the chemical described in the question. Common Pitfalls: Students sometimes confuse baking soda with baking powder or assume that anything associated with baking must be acidic. Others may select copper sulphate or magnesium oxide simply because they recognize the chemical names without recalling their uses. Another mistake is failing to connect the word vinegar with its underlying chemical name. To avoid these errors, remember that vinegar is sour and acidic due to acetic acid, whereas baking soda is mild and basic and copper sulphate and magnesium oxide are used in completely different contexts. Final Answer: The everyday substance that is essentially dilute acetic acid is Vinegar.

Question 17

In a simple displacement reaction between copper sulphate solution and iron metal, the reaction produces iron sulphate and which other substance as the displaced metal?

Accepted Answer

Introduction / Context: This question explores a classic example of a single displacement reaction in inorganic chemistry. When a more reactive metal is placed in a solution of a less reactive metal salt, the more reactive metal displaces the less reactive one from the solution. The reaction between iron metal and copper sulphate solution is a standard laboratory demonstration of this concept. Understanding which substance is formed alongside iron sulphate helps students visualize how metal reactivity and ionic exchange work in aqueous solutions. Given Data / Assumptions: - The reactants are copper sulphate solution and metallic iron. - The reaction is stated to produce iron sulphate as one of the products. - You must determine the other substance produced, which is the displaced metal from copper sulphate. - Options include vinegar, ash, baking soda, and copper. Concept / Approach: The key concept is the reactivity series of metals. Iron is more reactive than copper, so when iron metal is placed in copper sulphate solution, iron goes into solution as iron ions and copper is displaced as a solid metal. The balanced reaction can be written as Fe plus CuSO4 gives FeSO4 plus Cu. This shows that iron sulphate and copper metal are formed. Vinegar, ash, and baking soda are not metals and do not appear in the reaction between copper sulphate and iron. Therefore, by understanding displacement reactions and the reactivity series, you can identify copper as the correct displaced substance. Step-by-Step Solution: Step 1: Recall the general form of a displacement reaction where a more reactive metal displaces a less reactive metal from its salt solution. Step 2: Write the word equation for the given reaction: iron plus copper sulphate gives iron sulphate plus copper. Step 3: Recognize that in ionic form, Fe atoms lose electrons and become Fe2 plus ions, while Cu2 plus ions gain electrons and become copper metal. Step 4: Identify the products from the reaction equation as iron sulphate in solution and copper metal precipitating out. Step 5: Conclude that the substance forming alongside iron sulphate is copper, so Copper is the correct answer. Verification / Alternative check: You can verify this by performing or observing the experiment in a laboratory. When an iron nail is placed in blue copper sulphate solution, the blue color gradually fades as copper ions leave the solution and a reddish brown deposit of copper forms on the nail. The solution turns greenish due to the formation of iron sulphate. This visible change confirms that copper sulphate and iron react to produce iron sulphate and metallic copper. Textbook examples and reactivity series charts support this interpretation. Why Other Options Are Wrong: Vinegar is a solution of acetic acid and is not involved in a displacement reaction between copper sulphate and iron. Ash is a residue of combustion, not a metal produced in this reaction. Baking soda is sodium bicarbonate and does not appear in the reaction equation for iron and copper sulphate. None of these substances relate to the exchange of metal ions in this system. Only copper, the metal originally present as Cu2 plus ions in the copper sulphate solution, is displaced to form a solid metal product. Common Pitfalls: A common mistake is to look for a product that sounds chemical without checking the reaction pattern, which might lead some students to choose baking soda because it seems like a laboratory substance. Others may simply not recall the reactivity series and guess incorrectly. To avoid such errors, remember that displacement reactions involve swapping of metals between compounds and that iron is more reactive than copper. Therefore, copper is pushed out of solution and appears as a metal, while iron enters the solution as part of iron sulphate. Final Answer: The reaction of copper sulphate and iron produces iron sulphate and Copper as the displaced metal.

Question 18

In metallurgical industries, bauxite is primarily used as a raw material by which metal producing industry?

Accepted Answer

Introduction / Context: This question focuses on the link between important ores and the metal industries that depend on them. Bauxite is a widely known aluminium ore and is crucial for the production of aluminium metal through processes such as the Bayer and Hall Heroult processes. Recognizing that bauxite feeds the aluminium industry rather than iron, steel, or gold production is a basic general knowledge point in chemistry, geography, and industrial awareness. Exams often ask such straightforward questions to test whether you can associate key raw materials with the correct manufacturing sector. Given Data / Assumptions: - The mineral under consideration is bauxite. - The question asks which industry uses bauxite as its main raw material. - The options are aluminium, iron, steel, and gold industries. - It is assumed that you have encountered the term bauxite in discussions of aluminium extraction. Concept / Approach: The central concept is that bauxite is the principal ore of aluminium and contains hydrated aluminium oxides along with impurities. The aluminium industry uses bauxite as the starting raw material to obtain pure alumina, Al2O3, which is then electrolyzed to produce aluminium metal. Iron and steel industries rely on iron ores such as haematite and magnetite, not on bauxite. Gold mining uses completely different types of deposits and ores. Therefore, the logical approach is to connect bauxite directly with aluminium production based on standard metallurgical processes described in chemistry textbooks. Step-by-Step Solution: Step 1: Recall that bauxite is commonly referred to as the chief ore of aluminium. Step 2: Remember that bauxite is processed to remove impurities and obtain alumina in the Bayer process. Step 3: Note that alumina is then electrolyzed in molten form during the Hall Heroult process to produce aluminium metal. Step 4: Compare the industries listed in the options. Iron and steel production mainly use iron ore, and gold extraction uses different types of ore bodies. Step 5: Conclude that bauxite is specifically associated with the aluminium industry, so Aluminium is the correct answer. Verification / Alternative check: Verification can be done by examining standard metallurgy chapters or industrial case studies, which clearly identify bauxite as the starting material for aluminium production. They explain how bauxite is chemically treated to remove impurities and produce high purity alumina. In contrast, discussions of iron and steel refer to iron ores and blast furnace operations, and gold production is associated with mining and refining of gold bearing ores. Even general knowledge compilations and exam guides state that bauxite is used by the aluminium industry. This consistent information confirms that the correct industry is aluminium. Why Other Options Are Wrong: The iron industry uses haematite, magnetite, and similar iron ores as raw materials. The steel industry is built on refined iron and alloys, again starting from iron ores rather than bauxite. Gold extraction involves unique gold bearing ores and placer deposits, not aluminium rich bauxite. None of these industries list bauxite as their main raw material. Thus, iron, steel, and gold industries are not correct answers to this question. Common Pitfalls: A frequent mistake is to select steel because it is a very famous metal product, but this ignores the specific connection between bauxite and aluminium. Some students may also confuse bauxite with haematite or other ores if they do not review ore lists carefully. To avoid such errors, it is helpful to memorize key ore metal pairs, such as bauxite aluminium, haematite iron, and cassiterite tin, and to recall them whenever you see questions linking minerals to industries. Final Answer: Bauxite is used as a raw material primarily by the Aluminium industry.

Question 19

In household and industrial chemistry, synthetic detergents are mainly prepared from which type of starting material?

Accepted Answer

Introduction / Context: This question contrasts traditional soaps with modern synthetic detergents, an important topic in applied chemistry. Soaps are typically sodium or potassium salts of higher fatty acids derived from natural fats and oils, whereas synthetic detergents are produced from petrochemical sources. Understanding that synthetic detergents come from petroleum hydrocarbons rather than directly from animal or vegetable fats helps explain their different properties, such as performance in hard water and their widespread use in cleaning products. Given Data / Assumptions: - The focus is on synthetic detergents used for cleaning in homes and industries. - You are asked which starting material is used to prepare these synthetic detergents. - Options include potassium salts of higher fatty acids, sodium salts of higher fatty acids, hydrocarbons of petroleum, and glycerides. - It is assumed that you can distinguish between soaps and synthetic detergents based on their raw materials. Concept / Approach: The key concept is that soaps and synthetic detergents differ in both composition and source. Soaps are produced by saponification of fats and oils, creating sodium or potassium salts of long chain carboxylic acids. Synthetic detergents, however, are usually made from petrochemical hydrocarbons that are sulfonated or otherwise modified to create molecules with hydrophobic and hydrophilic parts. These detergent molecules are designed to work effectively in a range of water conditions, including hard water. Therefore, the correct starting material for synthetic detergents is hydrocarbons of petroleum, not the fatty acid salts or glycerides associated with traditional soap making. Step-by-Step Solution: Step 1: Recall that soaps are sodium or potassium salts of higher fatty acids obtained from natural fats and oils. Step 2: Remember that synthetic detergents are called synthetic because they are produced from artificially processed petrochemical feedstocks rather than directly from natural fats. Step 3: Identify hydrocarbons of petroleum as the key raw chemicals processed in the petrochemical industry to create detergent molecules. Step 4: Recognize that potassium and sodium salts of higher fatty acids and glycerides are closely related to soap formation, not to the main synthetic detergent routes. Step 5: Conclude that synthetic detergents are primarily prepared from hydrocarbons of petroleum, so that option is correct. Verification / Alternative check: You can verify this by reading any standard discussion of soaps and detergents in school chemistry textbooks. These chapters typically highlight that synthetic detergents, such as linear alkylbenzene sulfonates, are manufactured from petroleum based hydrocarbons. The text contrasts them with soaps derived from natural triglycerides in animal fats and vegetable oils. Industry information about surfactants also lists petrochemical hydrocarbons as starting materials. This consistent description confirms that hydrocarbons of petroleum are the correct answer. Why Other Options Are Wrong: Potassium salts of higher fatty acids and sodium salts of higher fatty acids are the basic chemical nature of soaps, not synthetic detergents. They are produced by reacting fats or oils with strong bases like sodium hydroxide or potassium hydroxide. Glycerides are esters of glycerol and fatty acids found in natural fats and oils and are also used in the production of soaps, not in the primary synthetic detergent routes. These substances are therefore associated with soap manufacture, not with the petrochemical synthesis of detergents. Common Pitfalls: Students sometimes confuse soaps and detergents and may select sodium salts of higher fatty acids because they recall that soap cleans. Others may not appreciate the difference between natural and synthetic sources. Another error is to choose glycerides due to their connection to fats without noting that the question specifically refers to synthetic detergents. To avoid these mistakes, remember that soaps are based on fatty acid salts from natural fats, while synthetic detergents are made from petroleum derived hydrocarbons processed in chemical plants. Final Answer: Synthetic detergents are mainly prepared from Hydrocarbons of petroleum.

Question 20

In basic chemistry of bases, which base is present in lime water that is often used in laboratory tests and in construction related chemistry?

Accepted Answer

Introduction / Context: This question deals with common bases in chemistry and their familiar names. Lime water is a simple laboratory reagent and is also related to materials used in construction, such as slaked lime. Knowing which base is present in lime water helps you connect theoretical chemical formulas with practical applications, such as tests for carbon dioxide gas and the setting of mortar. The question checks whether you can correctly identify calcium hydroxide as the dissolved base in lime water rather than confusing it with other hydroxides. Given Data / Assumptions: - The substance in question is lime water, a common term in school level chemistry. - You must identify which base is present in this solution. - Options include sodium hydroxide, magnesium hydroxide, calcium hydroxide, and ammonium hydroxide. - It is assumed that you know that lime water is a saturated aqueous solution of a specific slightly soluble base. Concept / Approach: Lime water is prepared by dissolving a small amount of calcium hydroxide, Ca(OH)2, in water to form a saturated solution. This mixture is distinct from sodium hydroxide solution, which is called caustic soda, and from ammonium hydroxide solution, which is aqueous ammonia. Magnesium hydroxide is very sparingly soluble and is usually encountered as a suspension called milk of magnesia, not as clear lime water. Therefore, the correct base present in lime water is calcium hydroxide. The approach is to associate each common name with its chemical formula and physical form in standard experiments. Step-by-Step Solution: Step 1: Recall that lime water is made by dissolving calcium hydroxide in water until a saturated solution is formed. Step 2: Remember that the chemical formula for calcium hydroxide is Ca(OH)2. Step 3: Recognize that sodium hydroxide solution is known as caustic soda and is much more soluble and strongly alkaline than lime water. Step 4: Note that magnesium hydroxide is typically a suspension called milk of magnesia, not the clear solution referred to as lime water. Step 5: Understand that ammonium hydroxide refers to aqueous ammonia, which has a distinctive smell and is not called lime water. Step 6: Conclude that lime water contains calcium hydroxide, so Calcium hydroxide is the correct answer. Verification / Alternative check: You can verify this by reviewing basic laboratory procedures for testing carbon dioxide gas. The standard test involves passing carbon dioxide through lime water, causing it to turn milky due to the formation of calcium carbonate. Instructions for this experiment clearly state that lime water is a solution of calcium hydroxide. Chemistry textbooks and practical manuals also define lime water as saturated calcium hydroxide solution. No authoritative source describes lime water as containing sodium hydroxide, magnesium hydroxide, or ammonium hydroxide, confirming that calcium hydroxide is correct. Why Other Options Are Wrong: Sodium hydroxide is a strong, highly soluble base known as caustic soda. It is not called lime water and has different uses. Magnesium hydroxide occurs mainly as a suspension and is related to antacids and other medicinal uses, not to lime water. Ammonium hydroxide is a solution of ammonia in water and has a strong pungent smell, quite different from lime water. None of these bases are accurately described by the term lime water in school level chemistry. Common Pitfalls: Students often mix up common names of bases, especially lime water, caustic soda, and milk of magnesia. Some may choose sodium hydroxide because it is a familiar strong base, ignoring the specific name lime. Others may not distinguish between suspensions and clear solutions. To avoid such errors, memorize the associations clearly: lime water equals calcium hydroxide solution, caustic soda equals sodium hydroxide, and milk of magnesia equals magnesium hydroxide suspension. Final Answer: The base present in lime water is Calcium hydroxide.

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