Consider the thermal decomposition of limestone: CaCO ₃( s ) CaO ( s ) + CO ₂( g ) Under which of the following temperature conditions does this reaction become spontaneous?

Step-by-step solution

The thermal decomposition of limestone requires continuous heat input to break the bonds in CaCO ₃ , making it an endothermic process ( H > 0 ). The reaction produces a gaseous product ( CO ₂ ) from a solid reactant, which increases the randomness of the system. Therefore, the entropy change is positive ( S > 0 ). According to the Gibbs free energy equation, G = H - T S . For a process to be spontaneous, G must be negative. Since both H and S are positive, the term T S must be greater than H to make G H S ). Answer