Answer to Question #161185 in Physical Chemistry for Hisham salihon

Question

The standard heats of formation of HCl (g) and HBr (g) are -92.0 kJ/mol and -36.4 kJ/mol respectively. Using this information, calculate ΔH for the following reaction:
Cl2 (g) + 2 HBr (g) → 2 HCl (g) + Br2 (g)

Answer 1

Cl2 (g) + 2 HBr (g) → 2 HCl (g) + Br2 (g)

Standard heats of formation:

Cl₂: 0

HBr: -36.4

HCl: -92.0

Br₂: 0

According to the equation:

HBr: -36.4 x 2

HCl: -92.0 x 2

 According to Hess’ law:

ΔH _rxn = -92.0 x 2 – (-36.4 x 2) = -111.2 (kJ/mol)