Question

The reaction of gaseous H2 and liquid Br2 to give gaseous HBr has ΔH = -17.4 kcal/mol (-72.8 kJ/mol) and ΔS = 27.2 (cal/mol · K) (114 J/(mol. K)). What type of information is ΔH in this context?

A) Enthalpy change
B) Entropy change
C) Internal energy change
D) Heat capacity change

Answer 1

The ΔH in the context of the reaction between H2 and Br2 represents the enthalpy change, which is -17.4 kcal/mol, indicating an exothermic reaction. It does not stand for heat capacity change.

Step-by-step explanation:

The ΔH for a reaction denotes the enthalpy change which represents the heat absorbed or released when a reaction takes place at constant pressure. It does not represent heat capacity change. In the reaction of gaseous H2 and liquid Br2 to give gaseous HBr, with ΔH = -17.4 kcal/mol (-72.8 kJ/mol), the reaction is exothermic as heat is released.

The negative value indicates that energy is released when hydrogen gas reacts with bromine gas to form hydrogen bromide gas. A positive ΔH would indicate an endothermic reaction, where heat is absorbed. The given ΔS value represents the entropy change, which quantifies the change in the disorder or randomness of the system as a result of the reaction.