OnlineCBT
Chemistry · THERMODYNAMICS
हिन्दीGiven below are statements regarding thermochemical conventions and Hess's Law: (A) By convention, the standard enthalpy of formation (\( \Delta_f H^\ominus \)) of an element in its most stable reference state is taken as zero. (B) Diamond is taken as the reference standard state of carbon with \( \Delta_f H^\ominus = 0 \). (C) Reversing a chemical equation changes the sign of its reaction enthalpy (\( \Delta_r H^\ominus \)) while keeping the numerical magnitude identical. (D) Enthalpy change is an intensive property because it does not depend on the stoichiometric coefficients of the balanced equation. Which of the above statements are correct?
Correct answer · Option 4
(A) and (C) only
Explanation
(A) and (C) are correct. (B) is false because graphite is the standard reference state (diamond has \( \Delta_f H^\ominus = +1.89\text{ kJ mol}^{-1} \)). (D) is false because enthalpy is an extensive property.
