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Heat of Formation

ΔrH and ΔrS...

Question

$Δ_{r} H$ and $Δ_{r} S$ for the reaction $M g O (s) + C (s) \to M g (s) + C O (g)$
are $491.18$ kJ $m o l^{- 1}$ and $197.67$ J $m o l^{- 1}$ respectively. Calculate the temperature at which Gibb's energy change will be zero.

A

2.4 K

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B

12.4 L

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C

312.4 K

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D

12.4 K

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Solution

The correct option is B 2.4 K
The given facts are :-
$M_{g} O (s) + C (s) \to M g (s) + C O (g)$
$△_{r} H = 491.18 K J / m o l, △ r s = 197.67 J / m o l$
Now, we have, $△ G = △ H - T △ S$
for $△ G = 0 \Rightarrow 0 = △ H - T △ S \Rightarrow T = \frac{△ H}{△ S} = \frac{491.18}{197.67} = 2.4 K$

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