Question

$40^{\circ}$ of $HI$ undergoes decomposition to $H _{2}$ and $I _{2}$ at $300 \,K . \Delta G ^{\ominus}$ for this decompostion reaction at one atmosphere pressure is ____$J \, mol ^{-1}$. [nearest integer]
(Use $R =8.31 \,J \,K ^{-1} \,mol ^{-1} ; \log 2=0.3010$. In $10=2.3, \log 3=0.477$)

Answer 1

teq $1-0.4 \frac{0.4}{2} \frac{0.4}{2}$
$K _{ p }=\frac{(0.2)^{\frac{1}{2}}(0.2)^{\frac{1}{2}}}{1-0.4}=\frac{0.2}{0.6}=\frac{1}{3}$
$\Delta G =\Delta G ^{\circ}+ RT \ln K =0$
$\Delta G ^{\circ}=- RT \ln K$
$\Rightarrow-8.31 \times 300 \times 2.3 \times \log \left(\frac{1}{3}\right)$
$= 2735 \,J/mol$