Question

Which of the following equations is used to obtain enthalpy change of a reaction?

• A. \(\Delta H = \sum \Delta H_P-\sum \Delta H_R\)
• B. \(\Delta H = \sum \Delta H_R-\sum \Delta H_P\)
• C. \(\Delta H = \sum \Delta H_P+\sum \Delta H_R\)
• D. \(\Delta H = \frac{\sum \Delta H_P}{\sum \Delta H_R}\)

Hint:

Enthalpy change is products minus reactants.

Answer 1

The Correct Option is A

Step 1: Apply state-function logic
For any property $X$ that is a state function, $\Delta X = X_{\text{final}} - X_{\text{initial}}$.

Step 2: Match
For a reaction, final means products and initial means reactants, so $\Delta H = \sum H_P - \sum H_R$, which is option (A).

Final Answer:
Enthalpy change is the sum for products minus the sum for reactants, option (A). \[ \boxed{\sum H_P-\sum H_R} \]