Question

question 1
given a δh of -112 kj, which statement is correct?
a the reaction is exothermic. heat is absorbed by the system from the surroundings.
b the reaction is exothermic. heat is released by the system to the surroundings.
c the reaction is endothermic. heat is released by the system to the surroundings.
d the reaction is endothermic. heat is absorbed by the system from the surroundings.

Explanation:

To determine the correct statement, we use the definition of enthalpy change ($\Delta H$):

• If $\Delta H < 0$, the reaction is exothermic (heat is released by the system to the surroundings).
• If $\Delta H > 0$, the reaction is endothermic (heat is absorbed by the system from the surroundings).

Given $\Delta H_{\text{rxn}} = -112\ \text{kJ}$ (negative), the reaction is exothermic, and heat is released by the system to the surroundings.

• Option A: Exothermic reactions release, not absorb, heat. Eliminate.
• Option B: Exothermic reactions release heat from the system to surroundings. Correct.
• Option C: Endothermic reactions absorb heat, but $\Delta H$ is negative (exothermic). Eliminate.
• Option D: Endothermic reactions absorb heat, but $\Delta H$ is negative (exothermic). Eliminate.

Answer:

B. The reaction is exothermic. Heat is released by the system to the surroundings.