Answer:
option C is the correct answer because its ΔHrxn is not equal to ΔH°f of the product.
Explanation:
The equation that has a ΔHrxn (change in enthalpy of reaction) that is not equal to ΔH°f (standard enthalpy of formation) of the product is option C: ½H2(g) + ½Cl2(g) → HCl(g).
In this equation, the reactants are hydrogen gas (H2) and chlorine gas (Cl2), and the product is hydrogen chloride gas (HCl). The ΔHrxn for this reaction would be the difference in enthalpy between the reactants and the product.
The standard enthalpy of formation (ΔH°f) is the enthalpy change when one mole of a compound is formed from its elements in their standard states at a given temperature and pressure. For example, the standard enthalpy of formation of HCl (ΔH°f HCl) would be the enthalpy change when one mole of HCl is formed from its elements (½ H2 and ½ Cl2) in their standard states.
In option C, the equation does not have the same number of moles on both sides. The reactants have only half a mole of H2 and half a mole of Cl2, while the product has one mole of HCl. This difference in stoichiometry leads to a difference in the number of moles involved in the reaction, resulting in a different enthalpy change (ΔHrxn) compared to the standard enthalpy of formation (ΔH°f) of the product.
Therefore, option C is the correct answer because its ΔHrxn is not equal to ΔH°f of the product.
