Question

A reaction occurs in a calorimeter, resulting in the starting and final temperatures shown below. What can you say about the reaction and the enthalpy change (ΔH) during the reaction?
Starting: 21.0 C
Final: 38.8 C

A. The reaction is endothermic and ΔH is positive.
B. The reaction is endothermic and ΔH is negative.
C. The reaction is exothermic and ΔH is positive.
D. The reaction is exothermic and ΔH is negative.

Answer 1

"The reaction is exothermic and ΔH is negative" can be understood about the reaction and the enthalpy change (ΔH) during the reaction.

Option: D

Explanation:

When the reaction is positive, the process becomes endothermic, i.e. heat appears to be consumed by the system because the reaction products are more enthalpic than the reactants. When the reaction is negative, on the other hand, the process is exothermic, which is the total decrease in enthalpy is caused by heat production. Here the initial temperature is 21.0 C but increase in final temperature to 38.8 C, because if some processes require heat, others must give off heat when they take place.