Question

Two $1$ litre containers contain $1$ mole each of the same gas at the same temperature. Gas of container $A$ is allowed to expand until the temperature of gas $A$ is reduced by half. Gas of container $B$ is compressed until the temperature of gas $B$ doubles. Both gases are then mixed together in a $2$ litre container. Find out the correct statement about the gasses?

• A. Both gases gain heat
• B. Both gases lose heat
• C. Gas $A$ loses heat to gas $B$
• D. Gas $B$ loses heat to gas $A$
• E. The equilibrium temperature of the gases is exactly one half the original starting temperature of the gases

Answer 1

The correct option is D Gas $B$ loses heat to gas $A$

Since the work done by the container A is positive, the temperature of the gas decreases.

Similarly the work done by the container B is negative, the temperature of the gas increases.

When the gases are mixed, the mixture tends to attain thermal equilibrium, thus attain a temperature in between the two temperatures. Thus the gas molecules of container A gain heat, and gas molecules of container B lose heat.