Chemistry MCQ Questions with Answer for all Competitive Exams

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.

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.

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.

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.

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

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

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

He →He⁺ +e^–

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.

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.

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.