Question

For the reaction : $2NOCl\left(g\right)⟶2NO\left(g\right)+{Cl}_2\left(g\right)$, The equilibrium constant at 400K, if ${\Delta H}^o=77.18kJ{mol}^{-1}$ and ${\Delta S}^o=0.122kJ{K}^{-1}{mol}^{-1}$ is:

• A. $1.97\times {10}^{-3}$
• B. $1.97\times {10}^{-2}$
• C. $1.97\times {10}^{-4}$
• D. $1.97\times {10}^{-1}$

Answer 1

Answer: (C)

$1.97\times {10}^{-4}$

Given the reaction: $2NOCl\left(g\right)\to 2NO\left(g\right)+C{l}_2\left(g\right)$

$\Delta G^o=\Delta H^o-T\Delta S^o$

$\Delta G^o=77.18-400\times 0.122kJmo{l}^{-1}$

$\Delta G^o=28.38kJmo{l}^{-1}$

$K=e^{\left(\frac{-\Delta G^o}{RT}\right)}$

$=1.97\times {10}^{-4}$

Hence, option C is correct.