Hydrogen bromide breaks down into diatomic hydrogen and bromine in the reaction shown.

Question

2HBr → H + Br
The energy of the reactant is 732 kJ/mol, and the energy of the products is 630 kJ/mol.
What is the total energy of the reaction? Is this reaction endothermic or exothermic?
(1 point)
2 2
–102 kJ/mol, endothermic
–102 kJ/mol, exothermic
102 kJ/mol, endothermic
102 kJ/mol, exothermic

Answer 1

To determine the total energy of the reaction, you can calculate the change in energy (ΔE) using the following formula:

\[ \Delta E = E_{\text{products}} - E_{\text{reactants}} \]

In this case, the energy of the reactants (HBr) is 732 kJ/mol and the energy of the products (H + Br) is 630 kJ/mol. Plugging in the values:

\[ \Delta E = 630 \text{ kJ/mol} - 732 \text{ kJ/mol} = -102 \text{ kJ/mol} \]

Since the change in energy (ΔE) is negative, this indicates that the reaction releases energy.

In terms of classifying the reaction:

• An exothermic reaction releases energy to the surroundings (ΔE is negative).
• An endothermic reaction absorbs energy from the surroundings (ΔE is positive).

Since ΔE = -102 kJ/mol, the reaction is exothermic.

Therefore, the correct answer is: –102 kJ/mol, exothermic.