Question

Calculate ${\Delta }_r{S}_{sys}^{\otimes }$ for the following reaction at 373 K:

$CO\left(g\right)+H_{2}O\left(g\right)\to C{O}_2\left(g\right)+H_2\left(g\right)$

${\Delta }_r{H}^{\otimes }=-4.1\times {10}^{4}J,{\Delta }_r{S}_{univ}^{\otimes }=56J/K$

• A. - 54 J/K
• B. -166 J/K
• C. +54 J/K
• D. +166 J/K

Answer 1

The correct option is A

- 54 J/K

${\Delta }_r{S}_{system}^{\otimes }=56={\Delta }_r{S}_{system}^{\otimes }+{\Delta }_r{S}_{surroundings}^{\otimes }$ and

${\Delta }_r{S}_{surroundings}^{\otimes }=\frac{-{\Delta }_r{H}_{system}^{\otimes }}{373}=\frac{4.1\times {10}^4}{373}=109.9J/K$

$\Rightarrow {\Delta }_r{S}_{system}^{\otimes }=56-109.9=-53.9J/K\approx -54J/K$