Q32 / 120 · VITEEE 2018 · Chemistry

The values of $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ for the reaction, $\mathrm{C}$ (graphite) $+\mathrm{CO}_{2}(g) \rightarrow 2 \mathrm{CO}(g)$ are $170 \mathrm{~kJ}$ and $170 \mathrm{JK}^{-1}$, respectively. This reaction will be spontaneous at

  • A
    $910 \mathrm{~K}$
  • Correct answer
    B
    $1110 \mathrm{~K}$
  • C
    $510 \mathrm{~K}$
  • D
    $710 \mathrm{~K}$

Solution

$\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}$ At equilibrium, $\Delta \mathrm{G}=0$ $$ \begin{array}{l} \Rightarrow 0=\left(170 \times 10^{3} \mathrm{~J}\right)-\mathrm{T}\left(170 \mathrm{JK}^{-1}\right) \\ \Rightarrow \mathrm{T}=1000 \mathrm{~K} \end{array} $$ For spontaneity, $\Delta \mathrm{G}$ is $-$ ve, which is possible only if $\mathrm{T}>1000 \mathrm{~K}$.

Hence, the correct answer is option: 'B'.

Relevant Questions