Assertion: Efficiency of any heat engine cannot be greater than the heat engine of Carnot's engine.

Reason: Heat flow never takes place from a body at lower temperature to a body at higher temperature.

Assertion: If the volume of a gas is increasing but the temperature of the gas is decreasing, then the heat given to the gas may be positive, negative or zero.

Reason: Heat given to a gas is a state function. It is not path function.

Assertion: First law of thermodynamics can be applied only for an ideal or real gas system.

Reason: First law of thermodynamics is nothing but law of conservation of energy.

Assertion: There are two processes : Process 1 is $pV=$ constant and process $2$ is $p{V}^2=$ constant. In both the processes volume of gas is increased from $V_1$ to $V_2$. Initial coordinates $\left(p_1\text{,} V_1\right)$ of the gas were the same. Then, more work is done by the gas in process $1$.

Reason: In second process pressure drops more rapidly with increase in volume.

Assertion: Any process taking place in the atmosphere is considered as an isobaric process.

Reason: Work done by the system in that case is $p_0\mathrm{\Delta }V$. Where, $p_0$ is atmospheric pressure.

Assertion: During melting of ice work done by surrounding on (ice + water) system is positive.

Reason: Volume of the given system decreases on melting of ice.

Assertion: Molar heat capacity cannot be defined for an isothermal process.

Reason: In isothermal process $\left(pV\right)$ versus $T$ graph is a dot.

Assertion: If the initial and the final volumes are equal, then work done by the gas is zero.

Reason In an isochoric process the initial and the final volumes are equal and work done by gas is zero.

Assertion: In adiabatic expansion the product of $p$ and $V$ always decreases.

Reason: In adiabatic expansion process, work is done by the gas at the cost of internal energy of gas.