Question

Use the bond energies to answer the question.

H–H = 432
H–O = 467
O=O = 495

Two H2 molecules combine with one O2 molecule, forming two water molecules (H2O) bonded as such: H–O–H. Which option shows the difference in total bond energy between the reactants and the products?

(1 point)
Responses

1,359
1,359

–7
–7

–509
–509

1,868

Answer 1

To determine the difference in total bond energy between the reactants and the products in the reaction \(2 \text{H}_2 + \text{O}_2 \rightarrow 2 \text{H}_2\text{O}\), we need to calculate the total bond energy for the reactants and the products.

**Step 1: Calculate the total bond energy of the reactants.**

The reactants are \(2 \text{H}_2\) and \(1 \text{O}_2\).

- For \(2 \text{H}_2\):
- Each \( \text{H}_2 \) has 1 H–H bond, so for 2 molecules:
\[
2 \times 432 \, \text{kJ} = 864 \, \text{kJ}
\]

- For \(1 \text{O}_2\):
- The \( \text{O}_2 \) has 1 O=O bond:
\[
1 \times 495 \, \text{kJ} = 495 \, \text{kJ}
\]

Total bond energy of reactants:
\[
864 \, \text{kJ} + 495 \, \text{kJ} = 1359 \, \text{kJ}
\]

**Step 2: Calculate the total bond energy of the products.**

The products are \(2 \text{H}_2\text{O}\) molecules.

- Each water molecule has 2 H–O bonds. So for \(2 \text{H}_2\text{O}\):
- Total number of H–O bonds = \(2 \times 2 = 4\)
\[
4 \times 467 \, \text{kJ} = 1868 \, \text{kJ}
\]

**Step 3: Calculate the difference in total bond energy.**

Difference = Total bond energy of reactants - Total bond energy of products:
\[
1359 \, \text{kJ} - 1868 \, \text{kJ} = -509 \, \text{kJ}
\]

Thus, the difference in total bond energy between the reactants and the products is \(-509 \, \text{kJ}\).

The final answer is:
**–509**