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In conversion of lime-stone to lime, CaCO3(s) → CaO(s) + CO2(g), the values of ΔH° and ΔS° are +179.1 kJ mol⁻¹ and 160.2 J/K mol⁻¹ respectively at 298 K and 1 bar. Assuming that ΔH° and ΔS° do not change with temperature, the temperature above which conversion of limestone to lime will be spontaneous is

1. 1118 K
2. 1008 K
3. 1200 K
4. 845 K

Correct answer: 1118 K

Solution

The conversion of limestone to lime becomes spontaneous when the Gibbs free energy change (ΔG) is negative, which occurs when the temperature exceeds the threshold calculated using the equation ΔG = ΔH - TΔS. By rearranging this equation to find the temperature at which ΔG equals zero, we can determine that the correct temperature is 1118 K.

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