Question

Which of the following statements regarding the heat of reaction is/are CORRECT?

• A. For endothermic reaction, it is positive.
• B. For exothermic reaction, it is negative.
• C. For exothermic reaction, it is positive.
• D. It is the enthalpy change for a process in which stoichiometric quantities of reactants, at a temperature and pressure, react completely in a single reaction to form products at the same temperature and pressure.

Hint:

Delta H is negative for exothermic and positive for endothermic reactions; heat of reaction is defined for complete stoichiometric conversion at the same T and P.

Answer 1

The Correct Option is A, B, D

At constant pressure $Q=\Delta H_{rxn}=H_{products}-H_{reactants}$, evaluated at complete stoichiometric conversion, same T and P (definition D confirmed). For endothermic, system draws heat in, $Q>0$ (A confirmed). For exothermic, system releases heat, $Q<0$ (B confirmed, C contradicted). \[ \boxed{A, B, D} \]