Q39 / 125 · BITSAT 2020 · Chemistry
$\Delta_{f} \mathrm{G}^{-}$ vs $\mathrm{T}$ plot in the Ellingham diagram slopes downward for the reaction
- A$\mathrm{Mg}+\frac{1}{2} \mathrm{O}_{2} \rightarrow \mathrm{MgO}$
- B$2 \mathrm{Ag}+\frac{1}{2} \mathrm{O}_{2} \rightarrow \mathrm{Ag}_{2} \mathrm{O}$
- Correct answerC$\mathrm{C}+\frac{1}{2} \mathrm{O}_{2} \rightarrow \mathrm{CO}$
- D$\mathrm{CO}+\frac{1}{2} \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}$
Solution
$\mathrm{C}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}(\mathrm{g}) ; \Delta \mathrm{S}$ increases.
Hence, as the temperature increases, $\mathrm{T} \Delta \mathrm{S}$ increases and hence $\Delta \mathrm{G}(\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S})$ decreases. In other words, the slope of the curve for formation of CO decreases. However, for all other oxides, it increases.
Hence, the correct answer is option: 'C'.