Chapter 15, Problem 12Q

(a)

To determine

To find: The change in entropy.

Explanation of Solution

As entropy is defined as change in heat at particular temperature, in an adiabatic process $\Delta Q=0$ .

Hence, entropy change $\text{Δ}S=\frac{\text{Δ}Q}{\text{Δ}T}=0$ .

It means entropy stay same

(b)

To determine

To find: The change in entropy.

Explanation of Solution

Formula used: $\Delta S=nRLn\frac{V_f}{V_i}$

Calculation: If $V_f>V_i$ then entropy will increase.

When we expand the gas iso-thermally then change in entropy $=nr\mathcal{l}n\left(v_2/v_1\right)$ .

If $v_2/v_1$ then entropy will increase.

Thus, entropy change = $\text{Δ}S=\frac{\text{Δ}Q}{\text{Δ}T}=increase.$