JEE PYQ: Thermodynamics Question 37
Question 37 - 2019 (11 Jan Shift 2)
The reaction $\text{MgO}(s) + \text{C}(s) \to \text{Mg}(s) + \text{CO}(g)$, for which $\Delta H^\circ = +491.1$ kJ mol$^{-1}$ and $\Delta S^\circ = 198.0$ JK$^{-1}$mol$^{-1}$, is not feasible at 298 K. Temperature above which reaction will be feasible is
(1) 2040.5 K
(2) 1890.0 K
(3) 2480.3 K
(4) 2380.5 K
Show Answer
Answer: (3)
Solution
$\text{MgO}(s) + \text{C}(s) \to \text{Mg}(s) + \text{CO}(g)$. For a reaction to be spontaneous, $\Delta G < 0$. $\Delta H^\circ - T\Delta S^\circ < 0$. $T > \dfrac{\Delta H^\circ}{\Delta S^\circ} = \dfrac{491.1 \times 1000}{198} = 2480.3$ K.
BETA
