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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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1 answer

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

1. Calculate the total bond energy of the reactants:

  • For CH4 (4 H–C bonds):

    • 4 bonds × 411 kJ/mol = 1644 kJ/mol

  • For Cl2 (4 Cl–Cl bonds):

    • 4 bonds × 242 kJ/mol = 968 kJ/mol

Total bond energy of reactants = 1644 kJ/mol + 968 kJ/mol = 2612 kJ/mol

2. Calculate the total bond energy of the products:

  • For CCl4 (4 C–Cl bonds):

    • 4 bonds × 327 kJ/mol = 1308 kJ/mol

  • For HCl (4 H–Cl bonds):

    • 4 bonds × 427 kJ/mol = 1708 kJ/mol

Total bond energy of products = 1308 kJ/mol + 1708 kJ/mol = 3016 kJ/mol

3. Compare the total bond energies:

  • Total energy of reactants: 2612 kJ/mol
  • Total energy of products: 3016 kJ/mol

Since the total bond energy of the reactants (2612 kJ/mol) is less than that of the products (3016 kJ/mol), energy is absorbed in the reaction, indicating that it is endothermic.

Conclusion:

The correct statement is:

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