JEE MAIN - Chemistry (2019 - 11th January Evening Slot - No. 17)
The reaction, MgO(s) + C(s) $$ \to $$ Mg(s) + CO(g), for which $$\Delta $$rHo + 491.1 kJ mol–1 and $$\Delta $$rSo = 198.0 JK–1 mol–1, is not feasible at 298 K. Temperature above which reaciton will be feasible is :
2480.3 K
2040.5 K
2380.5 K
1890.0 K
Explanation
We know,
$$\Delta $$Go = $$\Delta $$Ho - T$$\Delta $$So
For a reaction to be spontaneous $$\Delta $$Go must be negative i.e.,
T$$\Delta $$So > $$\Delta $$Ho
$$ \Rightarrow $$ T > $${{\Delta H^\circ } \over {\Delta S^\circ }}$$
$$ \Rightarrow $$ T > $${{491.1 \times 1000} \over {198}}$$
$$ \Rightarrow $$ T > 2480.3 K
$$\Delta $$Go = $$\Delta $$Ho - T$$\Delta $$So
For a reaction to be spontaneous $$\Delta $$Go must be negative i.e.,
T$$\Delta $$So > $$\Delta $$Ho
$$ \Rightarrow $$ T > $${{\Delta H^\circ } \over {\Delta S^\circ }}$$
$$ \Rightarrow $$ T > $${{491.1 \times 1000} \over {198}}$$
$$ \Rightarrow $$ T > 2480.3 K
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