Problem $3$: The heat of reaction: $\frac{1}{2}{H}_{2(g)}+\frac{1}{2}C{l}_{2(g)}HC{l}_{(g)}$ at $27C$ is $-22\mathrm{.}1$kcal.

Calculate the heat of reaction at $77C.$ The molar heat capacities at constant pressure at $27C$

for hydrogen, chlorine and $HCl$ are $6\mathrm{.}82,7\mathrm{.}70$ and $6\mathrm{.}80calmo{l}^{-1}$ respectively.

Answer: $-22\mathrm{.}1$ kcal