Sulfur reacts with oxygen to form sulfur dioxide (SO2 (g), Hf = - 296.8 kJ/mol) according to the equation below.

What is the enthalpy change for the reaction?

Use

We want:

S (s) + O2 (g) - - > SO2 (g)

given

1) S (s) + 3/2O2 (g) - - > SO3 (g) ∆H = - 395.8 kJ/mole

2) 2SO2 + O2 - - > 2SO3 (g) ∆H = - 198.2 kJ/mole

Reverse Equation 2) and divide by 2

SO3 (g) - - > SO2 (s) + 1/2O2 (g) ∆H = + 99.1 kJ/mole

Add Equation 1)

S (s) + O2 (g) - - > SO2 (g) ∆H = - 296.7 kJ/mole