alleryWhy is ∆rH of CaO + CO2 → CaCO3 not ∆fH of CaCO3?
AIt starts from compounds
BCO2 is not in standard state
CTwo moles of CaCO3 form
DThe reaction is endothermic
Answer & Solution
Correct answer: A. It starts from compounds
An enthalpy of formation must start from the elements, but here CaCO3 is made from two compounds.
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