Answer:
456 kJ
Step-by-step explanation:
CH₄ + 2Cl₂ ⟶ CCl₄ + 2H₂ ; ΔH = 45.6 kJ
Treat the heat as if it were a product in the equation. Then use the molar ratio (45.6 kJ/2 mol Cl₂) in the usual way.
Amount of energy = 20 mol Cl₂ × (45.6 kJ/2 mol Cl₂) = 456 kJ
You must add 456 kJ to react 20 mol of chlorine with excess methane.
