Question

*****S.O.S*****
Given the following information,

SO3 (g) + H2O(l) → H2SO4 (l) ΔH = -133 kJ

Pb(s) + PbO2 (s) + 2H2SO4(l) → 2PbSO4(s) + 2H2O(l) ΔH = -509 kJ

calculate the ΔH for the reaction below.

Pb(s) + PbO2 (s) + 2SO3 (g) → 2PbSO4 (s)
Select one:
a. -775kJ
b. 775kJ
c. 376kJ
d. -376kJ

Answer 1

Using the hess's law, there appears to be nothing to change in the reactions, except for the first one. You are looking for 2SO3 not SO3, so you must multiply your first equation by 2.

Answer 2

Then just add up the enthalpy's

Answer 3

Thanks. We haven't encountered Hess' Law yet.

Answer 4

Alright, it's actually a little confusing. But in your question it's used a lot simpler.