Which the following statements are correct ?

Options

A. Two bodies at different temperature `T_(1)` and `T_(2)` are brought in thermal contact. When thermal equilibrium is attained, the temperature of each body is `(T_(1) + T_(2))//2`.
B. The coolant used in a car or a chemical or nuclear plant should have high specific heat.
C. Vapour in equlibrium with its liquid at a constant temperature does not obey Boyle's law.
D. Two vessels `A` and `B` of equal capacity are connected to each other by a stop cock. Vessel `A` contains a gas at `0^(@)C` and 1 atm pressure. Vessel `B` is completely evacuated. When the stop cock is opened, the final pressure of gas in each vessel will be 0.5 atm.

Answer

B, C, D

Explanation

Statement `(a)` is incorrect. It is true only if the two bodies have the same thermal capacity.
Statement `(b)` is correct. The coolant is used to prevent the engine or the nuclear plant from becoming too hot. The heat absorbed by a substance per unit mass is directly proportional to its specific heat. Therefore if a coolant has a high specific heat, it will remove a large amount of heat from the engine or the nuclear plant.
Statement `(c)` is correct. If the volume of vapour is decreased, at a constant temperature a part of the vapour will condense into liquid such that the vapour pressure remains unchanged. In other words. the pressure does not increase but the volume of vapour decreases.
Statement `(d)` is also correct. Since the vessels are of the same capacity, the volume occupied by the gas is doubled, hence the pressure reduces to half.