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- Question
Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?
Options- A. Element with 18 neutrons and 20 protons
- B. Element with 19 neutrons and 18 protons
- C. Element with 19 neutrons and 20 protons
- D. Element with 18 neutrons and 22 neutrons
- Correct Answer
- Element with 18 neutrons and 22 neutrons
ExplanationIsobar: one of two or more atoms having equal atomic weights but different atomic numbers.Mass number Electrons NeutronsCalcium 40 20 20Argon 40 18 22 - 1. Which of the following bonds are weakest in nature?
Options- A. Single bond
- B. Double bond
- C. Triple bond
- D. Hydrogen bond Discuss
- 2. Which of the following substances cause temporary hardness in water? 1. Mg(HCO3)2 2. Ca(HCO3)2 3. CaCl2 4. MgSO4
Options- A. 3 and 4
- B. 2and 3
- C. 1 and 4
- D. 1 and 2 Discuss
- 3. Which one of the following is not a characteristic of a compound?
Options- A. Composition is variable.
- B. All particles of compound are of only one type.
- C. Particles of compound have two or more elements.
- D. Its constituents cannot be separated by simple physical methods. Discuss
- 4. Which one of the following is the correct relation between the Kelvin temperature (T) and the Celsius temperature (fc)?
Options- A. These are two independent temperature scales
- B. T = tc
- C. T = tc - 273.15
- D. T = tc + 273.15 Discuss
- 5. Why is argon gas used along with tungsten wire in an electric bulb?
Options- A. To increase the life of the bulb
- B. To reduce the consumption of electricity
- C. To make the emitted light colored
- D. To reduce the cost of the bulb Discuss
- 6. Consider the following constituent gases of the atmosphere : 1. Argon 2. Neon 3. Helium 4.Ceirbon dioxide Which one of the following is the correct ascending sequence of the above gases in terms of the volume percentage?
Options- A. 1-3-2-4
- B. 1-4-2-3
- C. 4-2-3-1
- D. 2-4-1-3 Discuss
- 7. The most abundant element in the earth's atmosphere is
Options- A. Argon
- B. Nitrogen
- C. Oxygen
- D. Krypton Discuss
- 8. Chemical composition of cement is
Options- A. Limestone and Clay
- B. Limestone, Clay and Gypsum
- C. Limestone and Gypsum
- D. Clay and Gypsum Discuss
- 9. A radio-active substance has a half life of six months. Three-fourth of the substance will decay in ______.
Options- A. Six months
- B. Ten months
- C. Twelve Months
- D. Twenty four months Discuss
- 10. Ozone is an ______ of oxygen.
Options- A. Allotrope
- B. Isotope
- C. Isobar
- D. Isotone Discuss
Chemistry problems
Search Results
Correct Answer: Hydrogen bond
Correct Answer: 1 and 2
Explanation:
There are two types of water hardness: temporary and permanent hardness. Temporary hardness is due to the presence of calcium hydrogen carbonate Ca(HCO3)2(aq) and magnesium hydrogen carbonate Mg(HCO3)2(aq).
Correct Answer: All particles of compound are of only one type.
Explanation:
A mixture is made from different substances that are not chemically joined.Compound:
?Two or more elements combine together chemically to form a new substance called compound.
?The different elements are chemically joined together.?Compounds are homogeneous, i.e. their properties are the same throughout
?The compound has properties different from the elements it contains.
?It can only be separated into its elements using chemical reactions. (not using physical methods)
?During the formation of a compound from its elements, a certain amount of energy in the form of heat, light, electricity is either absorbed or evolved
Correct Answer: T = tc + 273.15
Explanation:
Lord Kelvin, working in Scotland, developed the Kelvin scale in 1848. His scale uses molecular energy to define the extremes of hot and cold. Absolute zero, or 0 K, corresponds to the point at which molecular energy is at a minimum. The Kelvin scale is preferred in scientific work, although the Celsius scale is also commonly used. Temperatures measured on the Kelvin scale are reported simply as K, not °K.
T (in °C) + 273.15 = T (in K)
T (in K) ? 273.15 = T (in °C)
Correct Answer: To increase the life of the bulb
Explanation:
Argon gas is used in fluorescent and incandescent light bulbs to stop the oxygen in the light bulbs from corroding the hot tungsten filament.
The use of argon in light bulbs prevents the evaporation of the tungsten filaments, which results in increased light bulb life.
Argon is also used to create an inert atmosphere for growing semiconductor crystals, arc welding and for processes that need protection from other kinds of atmospheric gases.
Correct Answer: 1-4-2-3
Explanation:
Correct Answer: Nitrogen
Correct Answer: Limestone, Clay and Gypsum
Correct Answer: Twelve Months
Correct Answer: Allotrope
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