Question -
In the conversion of limestone to lime: CaCO3(s)→CaO(s)+CO2(g) The values of △H∘ and △S∘ are 179.1 kJ mol−1 and 160.2 J/K respectively at 298 K and 1 bar. Assuming △H∘ and △S∘ remains constant with temperature, at what temperature will the conversion of limestone to lime be spontaneous?
Options:
A .  1118 K
B .  1008 K
C .  1200 K
D .  845 K
Answer: Option A : A What is the criteria for spontaneity? The △G∘ value. We know that: △G∘ = △H∘ - T△S∘ For spontaneous reactions △G∘ = -ve △G∘ = △H∘ - T△S∘ ∴△H∘< T△S∘ Or T > △H∘△S∘ > 179.10×103160.2 > 1118 K
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