Question

At $320K$, a gas $A_2$ is $20$% dissociated at $A\left(g\right)$. The standard free energy change at $320K$ and $1$ atm in $J$ ${mol}^{-1}$ is approximately:
($R=8.314J{K}^{-1}$ ${mol}^{-1};\ln 2=0.693;\ln 3=1.098$)

• A. 1844
• B. 2068
• C. 4281
• D. 4763

Answer 1

The correct option is C 4281

$A_{2\left(g\right)}\leftrightharpoons 2A_{\left(g\right)}$
$1$ $0$
$1-1\times \frac{20}{100}$$2\times \frac{20}{100}$

$0.8$ $0.4$
$K_P=\frac{{\left(P_A\right)}^2}{\left(P_{A_2}\right)}=\frac{0.4\times 0.4}{0.8}=0.2$
$\Delta G^0=-2.03\times 8.314\times 320\times lo{g}_{10}0.2=4281J/mole$