Question

One mole of an ideal monoatomic gas expands isothermally against constant external pressure of 1 atm from initial volume of 1L to a state where its final pressure becomes equal to external pressure. If initial temperature of gas is 300 K then total entropy change of system in the above process is:

• A. $0$
• B. $Rln\left(24.6\right)$
• C. $Rln\left(2490\right)$
• D. $\frac{3}{2}Rln\left(24.6\right)$

Answer 1

The correct option is B $Rln\left(24.6\right)$

$1atm\underset{}{\overset{Isothermal}{\to }}1atm$

$1L$

$300K$ $300K$

$△S=C_v\ln \left(\frac{T_2}{T_1}\right)+R\ln \left(\frac{V_2}{V_1}\right)$

$T_1=T_2$

So

$△S=R\ln \left(\frac{V_2}{V_1}\right)$

$PV=$ const for this process

$P_1{V}_1=P_2{V}_2$

$1\times 1=1\times V_2$

$V_2=1lit$

$△S=0$