Question

Bond: H-H Cl-Cl H-Cl
Bond Energy: 432 239 427

Consider the reaction Hsmall2 + Clsmall2 > 2HCl

Is this reaction endothermic or exothermic based on the information in the table? Choose the answer below that supports your claim.

The reaction is exothermic because the total bond energy of the equation is 183 kJ.
The reaction is exothermic because the total bond energy of the equation is -183 kJ.
The reaction is endothermic because the total bond energy of the equation is 183 kJ.
The reaction is endothermic because the total bond energy of the equation is -183 kJ

Answer 1

To determine whether the reaction \( H_2 + Cl_2 \rightarrow 2HCl \) is exothermic or endothermic, we need to consider the bond energies given in the question.

First, we'll calculate the bond energy for the bonds broken on the reactants side and the bonds formed on the products side:

1. **Bonds Broken:**
- 1 \( H-H \) bond: 432 kJ
- 1 \( Cl-Cl \) bond: 239 kJ

Total energy for bonds broken:
\[
432 \, \text{kJ} + 239 \, \text{kJ} = 671 \, \text{kJ}
\]

2. **Bonds Formed:**
- 2 \( H-Cl \) bonds: 2 × 427 kJ = 854 kJ

Total energy for bonds formed:
\[
854 \, \text{kJ}
\]

Now, we can calculate the overall energy change for the reaction:

\[
\text{Energy Change} = \text{Total Energy of Bonds Broken} - \text{Total Energy of Bonds Formed}
\]
\[
\text{Energy Change} = 671 \, \text{kJ} - 854 \, \text{kJ} = -183 \, \text{kJ}
\]

Since the energy change is negative (-183 kJ), this indicates that the reaction releases energy, making it **exothermic**.

Based on this information, the correct answer is:

**The reaction is exothermic because the total bond energy of the equation is -183 kJ.**