The question
Name: ______________________ Date: ____________ Chlorinating methane: bonds and an energy diagram (4 points)
Data table
Average bond enthalpies
Methane reacts with chlorine in light: CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g).
| Bond | Bond enthalpy (kJ/mol) |
|---|---|
| C–H | 413 |
| Cl–Cl | 242 |
| C–Cl | 328 |
| H–Cl | 431 |
(a) Calculate the value of ΔH for the reaction using the bond enthalpies in the table. [1 point]
(b) Draw an energy diagram for the reaction. Label the reactants, the products and ΔH, and show an activation energy. [1 point]
(c) Using enthalpies of formation, ΔH° for the reaction is −99.4 kJ/mol. Explain why the value from part (a) differs from this value. [1 point]
(d) Explain, in terms of bonds broken and bonds formed, why the reaction is exothermic. [1 point]