Metallic mercury is obtained by roasting mercury (II) sulphide in a limited amount of air. Estimate the temperature range in which the standard reaction is product - favoured.
$H g S (s) + O_{2} (g) \to H g (l) + S O_{2} (g)$
$△ H^{o} = - 238.6 k J / m o l e a n d △ S^{o} = + 36.7 J / m o l e \cdot K$

When

T > 200 K

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When

T > 300 K

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At all temperatures

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None of these

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Solution

The correct option is C At all temperatures
Assume that $△ H a n d △ S$ values do not depend on temperature.

As $△ H^{0}$ is negative and $△ S^{0}$ is positive, using the equation $△ G^{0} = △ H^{0} - T △ S^{0}$

$△ G^{0}$ should be negative so the reaction is product-favoured.

$\Rightarrow △ H^{0} - T △ S^{0} < 0$

In the question $△ H^{0}$ is negative and $△ S^{0}$ is positive and we know temperature is always positive. So, $△ H^{0} - T △ S^{0}$ will be negative for all temperatures.

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Spontaneity

Standard XIII Chemistry

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Metallic mercury is obtained by roasting mercury (II) sulphide in a limited amount of air. Estimate the temperature range in which the standard reaction is product - favoured. HgS(s)+O2(g)→Hg(l)+SO2(g) △Ho=−238.6 kJ/mole and △So=+36.7 J/mole⋅K