Question

If one mole of an ideal gas $(C_{p,m}=\frac{5}{2}R)$ is expanded isothermally at 300 K until it's volume is tripled change in entropy of gas is R in 3 if above expansion is carried out freely $(P_{ext}=0)$ then find $\Delta S$?

• A. -R in 3
• B. R in 2
• C. R in 3
• D. None of these

Answer 1

The correct option is C R in 3

$\begin{array}{c}\text{We know that}\\ \Delta S=CV\ln \frac{T_2}{T_1}+R\ln \frac{V_2}{V_1}\\ CV\ln 1+R\ln \frac{V_2}{V_1}\\ 0+R\ln 3\end{array}$

Option C is correct answer.