2. Use Hess’s law and the following reactions to calculate the enthalpy change for AC A  B H=+34 kJ C  B H=+82 kJ

Question

1.      Use Hess’s law and the following reactions to calculate the enthalpy change for    AàC

A à B  DH=+34 kJ

C à B   DH=+82 kJ

Answer 1

A → C is a 2 step process:

A → B: Step 1, ΔH is +34 kJ

B → C: Step 2, ΔH is -82 kJ because this step is a reverse of C → BΔ

Δ H reaction=ΔH of Step 1 + ΔH of Step 2

Δ H=34 - 82 or -48 kJ