Question

Chemical Reactions Unit Test
14 of 1814 of 18 Items













Question
Use the table to answer the question.

Reaction CH4 + 4Cl2 → CCl4 + 4HCl
Reactants Products
Bonds Present
4 H–C

4 Cl–Cl

4 C–Cl

4 H–Cl

Energy of Bonds Broken (Reactants) / Formed (Products)

4 × 411 kJ/mol

4 × 242 kJ/mol

4 × 327 kJ/mol

4 × 427 kJ/mol

Which statement about the change in bond energy of this reaction is correct?

(1 point)
Responses

The reaction is exothermic because the energy of each bond in the reactants is greater than the energy of a bond in the products.
The reaction is exothermic because the energy of each bond in the reactants is greater than the energy of a bond in the products.

The reaction is endothermic because the total bond energy of the reactants is greater than the total bond energy of the products.
The reaction is endothermic because the total bond energy of the reactants is greater than the total bond energy of the products.

The reaction is exothermic because the total bond energy of the reactants is less than the total bond energy of the products.
The reaction is exothermic because the total bond energy of the reactants is less than the total bond energy of the products.

The reaction is endothermic because the energy of each bond in the reactants is less than the energy of a bond in the products.
The reaction is endothermic because the energy of each bond in the reactants is less than the energy of a bond in the products.
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Answer 1

To determine whether the reaction is exothermic or endothermic, we need to consider the energy of the bonds broken in the reactants and the energy of the bonds formed in the products.

The given reaction is:
\[ \text{CH}_4 + 4\text{Cl}_2 \rightarrow \text{CCl}_4 + 4\text{HCl} \]

Now, let's break it down:

1. **Calculation of Bond Energy of Reactants:**
- In the reactants:
- Methane (CH4) has 4 C–H bonds.
- Chlorine (Cl2) has 4 Cl–Cl bonds.
- The total bond energy for reactants:
\[
\text{Total bond energy (reactants)} = (4 \times 411 \, \text{kJ/mol}) + (4 \times 242 \, \text{kJ/mol})
\]
\[
= 1644 \, \text{kJ/mol} + 968 \, \text{kJ/mol} = 2612 \, \text{kJ/mol}
\]

2. **Calculation of Bond Energy of Products:**
- In the products:
- Carbon tetrachloride (CCl4) has 4 C–Cl bonds.
- Hydrogen chloride (HCl) has 4 H–Cl bonds.
- The total bond energy for products:
\[
\text{Total bond energy (products)} = (4 \times 327 \, \text{kJ/mol}) + (4 \times 427 \, \text{kJ/mol})
\]
\[
= 1308 \, \text{kJ/mol} + 1708 \, \text{kJ/mol} = 3016 \, \text{kJ/mol}
\]

3. **Comparison of Total Bond Energies:**
- Total bond energy of reactants = 2612 kJ/mol
- Total bond energy of products = 3016 kJ/mol

Since the energy of the bonds in the products is greater than the energy of the bonds in the reactants, the reaction requires energy (it absorbs energy) and is therefore **endothermic**.

The correct answer is:
**The reaction is endothermic because the total bond energy of the reactants is less than the total bond energy of the products.**