Chemistry MCQ Questions with Answer for all Competitive Exams

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Chemistry MCQ Questions with Answer


Q1. Atomic theory‘ of the matter was given by

(a) Avogadro

(b) Dalton

(c) Newton

(d) Pascal

Answer: (b)

Explanation: Atomic theory of matter was given by John Dalton. According to this theory, the matter is made up of extremely small indivisible and indestructible particles called Atoms.

Q2. An ideal gas is one which obeys ​

(a) ​Gas laws ​

(b) ​Boyle’s laws ​

(c) ​Charle’s law ​

(d)​ Avogadro’s law

Answer: (a)​

Explanation: A gas, when kept at a constant temperature, would obey the gas laws exactly. The gas laws are Charle’s law, Boyle’s law, and Gay-Lussac’s law.

Q3. The nucleus of an atom consists of.

(a) Proton

(b) Neutron

(c) Proton and Neutron

(d) Electron, Proton and Neutron

Answer: (c)

Explanation: All atoms except the hydrogen atom, are composed of three fundamental particles, namely electrons, protons, and neutrons. Protons and neutrons are present inside the nucleus.

Q4. Which one of the following can be used to confirm whether drinking water contains a gamma-emitting isotope or not?

(a) Microscope

(b) Lead plate

(c) Scintillation counter

(d) Spectrophotometer

Answer: (c)

Explanation: Scintillation counter (scintillometer): An instrument that measures gamma radiation. It is also used in airborne and ground radiometer surveys. This instrument utilizes the flash of light emitted when the atoms of a suitable ‘ phosphor’ are energized by gamma rays. The scintillations are detected by a light-sensitive cathode.

Q5. Which gas is responsible for the swelling of bread? ​

(a) ​Oxygen

​(b) ​Carbon monoxide

​(c) ​Carbon dioxide ​

(d)​ Ammonia

Answer: ​(c)​

Explanation: Carbon dioxide is responsible for the swelling of bread.

Q6. LPG is a mixture of ​

(a)​ C6H12 + C6H6

(b) ​C4H10 + C3H8

(c)​ C2H2 + C2H4

(d)​ CH4 + C2H4

Answer: (b)​

Explanation: LPG is a mixture of C4H10 (Butane), C3H8 (propane) and C2H6 (ethane). Main constituent is butane (C4H10).

Q7. When the Helium atom loses an electron, then it becomes–

(a) Proton

(b) Positive Helium ion

(c) Negative Helium ion

(d) Alpha Particle

Answer: (b)

Explanation: When the Helium atom loses an electron, then it forms a positive helium ion.

He →He+ +e

Also Read: Physics MCQ Questions  with Answer for all Competitive Exams

Q8.Yellowcake’, an item of smuggling across the border is

(a) A crude form of heroin

(b) A crude form of cocaine

(c) Uranium oxide

(d) Unrefined gold

Answer: (c)

Explanation: Uranium oxide is smuggled across borders in the form of yellowcake. Uranium oxide is produced by refining tons of dirt (ore) containing uranium to produce “Yellowcake“. Typically yellow cake contains 80% of uranium oxide, which melts at approximately 2878°C whereas modern yellow cake contains 70 to 90% triuranium oxide (U3O8) by weight. Yellowcake is used in the preparation of uranium fuel for the nuclear reactor. Uranium obtained from yellowcake also used in making many types of illegal nuclear explosives which is very dangerous to mankind.

Q9. Which of the following is a radioactive element?

(a) Cobalt

(b) Uranium

(c) Argon

(d) Chromium

Answer: (b)

Explanation: Elements having atomic no. greater than 82 are radioactive in nature. In the given options, the Atomic Number of Uranium is 92 so, it is a radioactive element.

Q10. The — OH group of — COOH can be replaced by Cl using

(a) PCl5

(b) HOCl

(c) Cl2

(d) HCl

Answer: (a)

Explanation: The -OH group of -COOH can be replaced by Cl using PCl5, PCl3 or SOCl2. In the given options PCl5 is the correct answer.

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