Question

$K _{ p }$ has the value of $10^{-6} \,atm ^{3}$ and $10^{-4} \,atm ^{3}$ at $298 \,K$ and $323 \,K$ respectively for the reaction
$CuSO _{4} \cdot 3 H _{2} O ( s ) \rightleftharpoons CuSO _{4}( s )+3 H _{2} O ( g )$
$\Delta_{ r } H ^{\circ}$ for the reaction is:

• A. 7.7 kJ/mol
• B. -147.41 kJ/mol
• C. 147.41 kJ/mol
• D. None of these

Answer 1

Answer: (C)

In $\frac{ K _{ P _{2}}}{ K _{ p _{1}}}=\frac{\Delta H ^{\circ}}{ R }\left[\frac{1}{ T _{1}}-\frac{1}{ T _{2}}\right]$
= In $\left(\frac{10^{-4}}{10^{-6}}\right)=\frac{\Delta H ^{\circ}}{8.314}\left[\frac{25}{298 \times 323}\right]$
$\Delta_{ r } H ^{\circ}=147.41 \,kJ / mol$