Question 1

Definitions (alloys): What are amalgams? Base your answer on alloy composition and a distinctive liquid component. Choose the correct definition.

Accepted Answer

Given data Term: Amalgam. Concept/Approach An amalgam is an alloy in which mercury is a constituent, typically forming liquid or soft solid solutions with other metals (e.g., Ag, Au, Zn, Sn). Final Answer Alloys which contain mercury as one of the contents

Question 2

Petroleum products (LPG composition): What are the main constituent gases of Liquefied Petroleum Gas used for cooking and heating? LPG is a mixture of low–molecular-weight hydrocarbons stored as a liquid under moderate pressure. Choose the correct p…

Accepted Answer

Given data LPG = Liquefied Petroleum Gas used domestically and industrially. Stored under pressure; vaporized for burning. Concept/Approach LPG is formulated primarily from propane and butane (including isobutane). Methane is the main component of CNG/LNG, not LPG. Reasoning • Propane and butane liquefy at modest pressures and ambient temperatures → ideal for cylinders.• Heavier components like hexane/nonane are not used due to poor volatility. Common pitfalls Mistaking LPG (propane–butane) for CNG/LNG (methane). Final Answer Propane (C3H8) and butane (C4H10)

Question 3

Water purification chemistry: Why is potassium permanganate (KMnO4) used in treating/purifying drinking water? Focus on its chemical action on microbes and organic contaminants during disinfection. Choose the correct reason.

Accepted Answer

Given data Reagent: Potassium permanganate (KMnO4). Use case: Disinfection/oxidation in water treatment. Concept/Approach KMnO4 is a strong oxidising agent. Oxidation damages microbial cell components and converts certain dissolved organics/iron/manganese to insoluble forms that can be removed. Reasoning KMnO4 + organics/Fe2+/Mn2+ → oxidised products + MnO2(s).Disinfection efficacy stems from oxidation, i.e., its chemical sterilising action. Common pitfalls Confusing its role as reducing agent (incorrect here) or thinking it merely “dissolves impurities”. Final Answer It is an oxidising agent

Question 4

Environmental pollution (urban air): Which metal is a major pollutant in the air of large cities? Consider historical vehicular emissions and legacy contamination from fuels and industry. Choose the correct metal.

Accepted Answer

Given data Context: Big-city air quality, traffic-related emissions. Concept/Approach For decades, lead was emitted from leaded gasoline (tetraethyl lead). Though phased out in many countries, urban dust/soil often retains legacy lead; industrial sources also contribute. Reasoning Leaded petrol → exhaust aerosols with Pb compounds → ambient air/dust contamination. Common pitfalls Chromium and cadmium are industrial toxins but less ubiquitous in traffic-related ambient air than historical lead. Final Answer Lead

Question 5

Biominerals (pearls): What are the principal constituents of natural pearls? Identify the mineral phase and the organic matrix secreted by molluscs. Choose the correct pair.

Accepted Answer

Given data Object: Natural pearls (nacre). Concept/Approach Pearls consist mainly of aragonite (a crystalline form of CaCO3) arranged in platelets, bound by an organic protein–polysaccharide matrix called conchiolin. Reasoning Aragonite (mineral) + conchiolin (organic) → nacre's layered structure and luster. Common pitfalls Confusing aragonite with calcite (another CaCO3 polymorph) or pairing with unrelated salts. Final Answer Aragonite and conchiolin

Question 6

Metals (coinage group): Which of the following pairs does not contain any coinage metal? Coinage metals are Cu, Ag and Au in Group 11 of the periodic table. Choose the pair with zero coinage metals.

Accepted Answer

Given data Coinage metals: copper (Cu), silver (Ag), gold (Au). Concept/Approach Pairs containing any of Cu/Ag/Au include coinage metals and are therefore not correct. A pair of non-coinage metals (e.g., Zn and Sn) contains none. Reasoning Check each pair:• Silver & gold → both coinage (reject).• Copper & silver → both coinage (reject).• Copper & gold → both coinage (reject).• Zinc & tin → neither is coinage (accept). Final Answer Zinc and tin

Question 7

Periodic table (f-block): The actinide series comprises elements with which atomic-number range? Identify the standard range used in chemistry for actinides. Choose the correct range.

Accepted Answer

Given data Series: Actinides (5f-block). Concept/Approach Actinides start at actinium (Z = 89) and run through lawrencium (Z = 103), covering the 5f orbital filling sequence. Final Answer 89 to 103

Question 8

Physical properties: Which of the following metals is liquid under normal room conditions? Consider ambient temperature and standard pressure. Choose the correct metal.

Accepted Answer

Given data Condition: ~25 °C, 1 atm. Concept/Approach Only two elemental substances are liquid near room temperature: mercury (metal) and bromine (non-metal). Among the listed metals, mercury is the only one liquid at room temperature. Final Answer Mercury

Question 9

Alloys (bell metal): Bell metal is an alloy of which two metals? Identify the traditional composition used for bells with sonorous tone. Choose the correct alloy pair.

Accepted Answer

Given data Object: Bells and gongs. Concept/Approach Bell metal is a high-tin bronze, typically ~20–25% Sn and the balance Cu, giving hardness and resonance. Common pitfalls Confusing with brass (Cu–Zn) or cupronickel (Cu–Ni). Final Answer Tin and copper

Question 10

Reactive metals storage: Under which liquid is metallic sodium safely stored? Prevent rapid reaction with air moisture and oxygen. Choose the correct storage medium.

Accepted Answer

Given data Metal: Sodium (highly reactive alkali metal). Concept/Approach Sodium rapidly oxidises and reacts with water; it is stored immersed in an inert hydrocarbon such as kerosene/liquid paraffin that excludes air and moisture. Reasoning Water → violent reaction; alcohols → reactive; petrol is flammable/less standard. Final Answer Kerosene (liquid paraffin)

Question 11

Minerals (silicates): Quartz crystals used in clocks and electronics are chemically what compound? Identify the correct oxide making up quartz (rock crystal). Choose the correct compound.

Accepted Answer

Given data Material: Quartz crystals in oscillators/timekeeping. Concept/Approach Natural and synthetic quartz are crystalline silicon dioxide (SiO2), prized for piezoelectric properties used in stable frequency control. Final Answer Silicon dioxide (SiO2)

Question 12

Applied chemistry (LPG safety): Ethyl mercaptan is added to otherwise odourless LPG to impart a detectable smell. Identify the chemical family/element that characterizes ethyl mercaptan (ethyl thiol). Choose the correct element.

Accepted Answer

Given data LPG is naturally odourless; a smelly compound (ethyl mercaptan) is added for leak detection. Ask: The element/compound class that defines ethyl mercaptan. Concept/Approach Ethyl mercaptan is ethyl thiol (C2H5SH). Thiols are sulfur-containing analogues of alcohols (–SH group instead of –OH), responsible for the strong characteristic odour. Reasoning • The odorant used in LPG is a sulfur compound → answer is sulphur. • Halogens (Cl, F, Br) are not part of ethyl mercaptan's functional group. Final Answer Sulphur

Question 13

Materials: Name the property of a substance that absorbs moisture from air upon exposure. Focus on the phenomenon where solids pick up atmospheric water; in some cases they even dissolve in it. Choose the correct term.

Accepted Answer

Given data Observation: A solid exposed to air absorbs moisture. Task: Name that property. Concept/Approach Two related terms exist: hygroscopic (general tendency to absorb moisture) and deliquescent (absorbs so much water that it forms a solution). Among the given options, the correct specific term is deliquescence. Reasoning • Deliquescence → moisture absorption leading to dissolution (e.g., CaCl2, NaOH pellets). • Efflorescence is the opposite: losing water of crystallization. • Osmosis involves semipermeable membranes; desiccation is drying. Final Answer Deliquescence

Question 14

Water treatment (hardness): Removing permanent hardness of water by chemical addition. Select the compound that effectively removes Ca²⁺/Mg²⁺ hardness by precipitation. Choose the correct reagent.

Accepted Answer

Given data Permanently hard water contains Ca2+/Mg2+ (as chlorides/sulfates). Concept/Approach Adding sodium carbonate (washing soda) precipitates CaCO3/MgCO3, removing hardness ions from solution. Step-by-step • CaCl2 + Na2CO3 → CaCO3↓ + 2 NaCl • MgSO4 + Na2CO3 → MgCO3↓ + Na2SO4 Common pitfalls Chlorine/bleaching powder disinfect; KMnO4 is an oxidant, not a hardness remover. Final Answer Washing soda (Na2CO3)

Question 15

Minerals and ores: Monazite — identify the element for which it is an important ore. Think of rare earth/thorium-rich beach sands in India. Choose the correct element.

Accepted Answer

Given data Ore: Monazite (phosphate of rare earths). Concept/Approach Monazite sands are rich in rare earth elements and thorium; they are a traditional source of thorium compounds. Final Answer Thorium

Question 16

Basic classification: Which of the following is an element (not a compound/mineral)? Identify the choice consisting of a single chemical element in its pure form. Choose the correct option.

Accepted Answer

Given data Options include gemstones and one elemental form. Concept/Approach Diamond is pure crystalline carbon (an allotrope → element). Ruby/sapphire are corundum (Al2O3) with dopants; emerald is beryl (Be3Al2(SiO3)6). Final Answer Diamond

Question 17

Applied physics (lighting): The filament material of a typical incandescent electric bulb. Consider high melting point, strength at high temperature, and emissivity. Choose the correct material.

Accepted Answer

Given data Ask: Filament material for incandescent bulbs. Concept/Approach Tungsten (melting point ≈ 3422 °C) withstands high temperatures and has suitable mechanical properties when coiled, making it standard for filaments. Final Answer Tungsten

Question 18

Lubrication: Identify the material commonly used as a dry lubricant. Consider layered structures that shear easily. Choose the correct material.

Accepted Answer

Given data Task: Choose a lubricant material from common solids. Concept/Approach Graphite has layered sp2 sheets with weak interlayer forces; layers slide easily → excellent dry lubricant. Final Answer Graphite

Question 19

Electric bulbs (fill gas): Identify the gas usually filled in incandescent electric bulbs to protect the filament. Consider inertness and prevention of filament oxidation at working temperature. Choose the correct gas.

Accepted Answer

Given data Ask: Gas used inside incandescent bulbs. Concept/Approach Incandescent bulbs are filled with inert/neutral gases (commonly nitrogen, often mixed with argon) to prevent tungsten oxidation and to reduce filament evaporation. Common pitfalls Oxygen would quickly oxidize the filament; hydrogen/CO2 are not used for this purpose. Final Answer Nitrogen

Question 20

Everyday materials (cookware): Non-stick cooking utensils are coated with which polymer? Identify the standard low-friction, high-temperature resistant coating. Choose the correct coating.

Accepted Answer

Given data Product: Non-stick cookware. Concept/Approach Non-stick surfaces use polytetrafluoroethylene (PTFE), commonly called Teflon, due to its very low surface energy and thermal/chemical stability. Final Answer Teflon (PTFE)

General Science Questions