Question

Using your knowledge on Hess's law and the two equations given below, calculate the enthalpy change of the following reaction:

S(s) + O2(g) → SO2(g

S(s) + 3 2 O2(g) → SO3(g) ∆H = -395.2 kJ
2 SO2(g) + O2(g) → 2 SO3(g) ∆H = -198.2 kJ

Answer 1

Answer:

S(s) + O2(g) → SO2 (g) ∆H = ‐296.8 kJ

2SO2 + O2 → 2SO3 ∆H = ‐198.4 kJ

Write the equation for the formation of sulfur trioxide gas from sulfur solid and oxygen. What is the ∆H of that equation2 S(s) + 3 O2(g) → 2 SO3

We can use Hess’s Law to determine the enthalpy change of the overall reaction from the given reactions:

1. S(s) + O2 (g) → SO2 (g) ∆H = ‐296.8 kJ

2. 2 SO2 + O2 → 2 SO3 ∆H = ‐198.4 kJ

We now need to find a combination of reactions that when added up, gives us the overall reaction.