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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/mo

1 answer

To calculate the net energy change for the reaction, we need to find the total energy of the bonds broken in the reactants and the total energy of the bonds formed in the products.

  1. Calculate total energy of bonds broken (Reactants):

    • For CH4:
      • 4 H–C bonds: \( 4 \times 411 , \text{kJ/mol} = 1644 , \text{kJ/mol} \)
    • For Cl2:
      • 4 Cl–Cl bonds: \( 4 \times 242 , \text{kJ/mol} = 968 , \text{kJ/mol} \)
    • Total energy for bonds broken: \[ 1644 , \text{kJ/mol} + 968 , \text{kJ/mol} = 2612 , \text{kJ/mol} \]

  2. Calculate total energy of bonds formed (Products):

    • For CCl4:
      • 4 C–Cl bonds: \( 4 \times 327 , \text{kJ/mol} = 1308 , \text{kJ/mol} \)
    • For HCl:
      • 4 H–Cl bonds: \( 4 \times 427 , \text{kJ/mol} = 1708 , \text{kJ/mol} \)
    • Total energy for bonds formed: \[ 1308 , \text{kJ/mol} + 1708 , \text{kJ/mol} = 3016 , \text{kJ/mol} \]

  3. Calculate the net energy change:

    • \( \text{Net Energy Change} = \text{Energy of bonds broken} - \text{Energy of bonds formed} \) \[ \text{Net Energy Change} = 2612 , \text{kJ/mol} - 3016 , \text{kJ/mol} = -404 , \text{kJ/mol} \]

Thus, the net energy change for the reaction \( \text{CH}_4 + 4 \text{Cl}_2 \rightarrow \text{CCl}_4 + 4 \text{HCl} \) is -404 kJ/mol, indicating that the reaction is exothermic.