General Science (Chemistry) MCQs For WBCS Prelims and Mains P1

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16131. The highest amount of known element in the earth is

A

Hydrogen

B

Oxygen

C

Argon

D

Helium

B

Correct Answer: B. Oxygen
Explanation: In the earth the most abundant known element is Oxygen(O2). 46.6% of earth mass is Oxygen. In the Universe the most abundant known element is Hydrogen.

16142. Which set of condition represents the easiest way to liquify a gas?

A

Low-temperature and low pressure

B

High-temperature and high pressure

C

Low-temperature and high-pressure

D

Low-temperature and low pressure

C

Correct Answer: C. Low-temperature and high-pressure
Explanation: Low temperature decreases the energy of gaseous molecules bringing them closer, on the other hand increasing pressure also decreases the intermolecular distance thereby favouring the formation of liquid.

16153. The most abundant rare gas in the atmosphere is

A

Argon

B

Xenon

C

Helium

D

Neon

A

Correct Answer: A. Argon
Explanation:

Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in the Earth's atmosphere.

• Nitrogen — 78%
• Oxygen — 21%
• Argon — 0.93%

16164. Water gas is a mixture of

A

Carbon monoxide and Nitrogen

B

Carbon dioxide and Nitrogen

C

Carbon monoxide and Hydrogen

D

Carbon dioxide and Hydrogen

C

Correct Answer: C. Carbon monoxide and Hydrogen

16175. Which of the following gasses is most responsible for recent death in AMRI, Kolkata?

A

Methane

B

Hydrogen sulfide

C

Carbon dioxide

D

Carbon monoxide

D

Correct Answer: D. Carbon monoxide
Explanation: 89 people were dead in December, 2011

16186. Atoms with the same mass number but having different nuclear charges are called

A

Isochores

B

Isotones

C

Isotopes

D

Isobars

D

Correct Answer: D. Isobars
Explanation:

Isobars are atoms of different chemical elements that have the same number of nucleons (Nucleon is the collective term for protons and neutrons). Correspondingly, isobars differ in atomic number but have the same mass number. An example of a series of isobars would be ⁴⁰S, ⁴⁰Cl, ⁴⁰Ar, ⁴⁰K, and ⁴⁰Ca.

16197. The number of electrons present in H⁺ is

A

Zero

B

One

C

Two

D

Three

A

Correct Answer: A. Zero
Explanation:

Hydrogen atomic no 1, so electron present 1, after removal of 1 electron it produces H⁺ ion, so H⁺ ion has zero electrons.

16208. The strongest electropositive element is

A

Mg

B

K

C

Cs

D

Li

C

Correct Answer: C. Cs
Explanation:

Cesium (Cs) metal is at the last in the group of alkali metals, thus it is the most electropositive element. In Cs, there are many shells, and no. of electrons is more. But in the outermost shell, there is only one electron.

16219. Ethyl alcohol is completely mixed with water It can be separated from that mixture by

A

Fractional distillation

B

Allowing the water to evaporate

C

Using a separating funnel

D

Evaporation

A

Correct Answer: A. Fractional distillation

162210. Which of the following modes of expressing concentrations is independent of temperature?

A

Normality

B

Formality

C

Molarity

D

Molality

D

Correct Answer: D. Molality
Explanation:

Molality is a property of a solution and is defined as the number of moles of solute per kilogram of solvent. The SI unit for molality is mol/kg. A solution with a molality of 3 mol/kg is often described as '3 molal' or '3 m'. However, following the SI system of units, mol/kg or a related SI unit is now preferred.

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