Question

For the reaction $\frac{1}{8}{S}_{8\left(s\right)}+\frac{3}{2}{O}_{2\left(g\right)}\to {SO}_{3\left(g\right)}$, the difference of heat change at constant pressure and constant volume at ${27}^{0}C$ will be:

• A. +150 R
• B. -150 R
• C. +450 R
• D. -450 R

Answer 1

The correct option is B -150 R

difference between heat at constant pressure , i.e $\Delta H$

difference and heat at constant volume , i.e. $\Delta U$

$\therefore \Delta H-\Delta U=\Delta n_{gas}RT$

$\frac{1}{8}{S}_8\left(s\right)+\frac{3}{2}{O}_2\left(g\right)\rightleftharpoons S{O}_3\left(g\right)$

$\therefore \Delta n_{gas}=1-\frac{3}{2}=(-\frac{1}{2})$

$\therefore diff=\frac{-1}{2}\times R\times T$

$=\frac{-1}{2}\times R\times 300=-150R$