Chemistry - Study Mode

[#736] Nucleons are regarded as composites sub-particles known as
Correct Answer

(B) Quarks

Explanation

Solution: In quantum chromodynamics, nucleons are regarded as composites of three quarks (elementary particles) and pions are composites of two quarks. According to EOB’s rules, nucleons move as fermions while pions move as bosons.

[#737] Conduction band electrons have more mobility than holes because they
Correct Answer

(B) Experience collision less frequently

Explanation

Solution: When an electric field is applied, both the valence electrons and the free electrons move in the same direction. The hole direction is opposite to that of valence electron but the mobility is the same. Even for the same electric field, valence electrons cannot move as freely as the free electrons because its movement is restricted due to collisions. Therefore, the velocity of valence electrons is less compared to free electrons. In other words, the velocity of holes is less compared to free electrons. This means mobility is also less for a hole compared to free electron.

[#738] Which one of the following has greatest mass ?
Correct Answer

(C) Neutron

Explanation

Solution: Neutron has greatest mass. Proton is a subatomic particle with symbol p and positive electric charge of +1 elementary charge and mass slightly less than that of neutron.

[#739] Bleaching powder is used in drinking water as a/an
Correct Answer

(A) Disinfectant

Explanation

Solution: Bleaching powder, CaOCl 2 or calciumoxychloride is used to kill germs and bacteria of water because it contains chlorine element, which is good disinfecting agent.

[#740] The process of removing calcium and magnesium from hard water is known as
Correct Answer

(D) Water softening

Explanation

Solution: Softening is the process of removing the dissolved calcium and magnesium salts that cause hardness in water. Water softening is achieved either by adding chemicals that form insoluble precipitates or by ion exchange.