Application of Standard Enthalpy of Formation

[Phan Tran 1K]

I'm working through problem 8.99 in the 6th edition and I'm confused about how to apply finding the enthalpy of formation.

The problem is long, and parred down to the relevant information it reads:
A technician carries out the reaction 2 SO2(g) + O2(g) S 2 SO3(g) at 25 C and 1.00 atm in a constant-pressure cylinder fi tted with a piston. Initially, 0.030 mol SO2 and 0.030 mol O2 are present in the cylinder. (e) How much enthalpy is exchanged, and does it leave or enter the system?

I know I have to use the formula for the standard enthalpy of formation, but I don't know whether to it like so:
deltaH=0.030molSO2(2(-296.83 kJ/mol)-(2(-395.72 kJ/mol))
or like this
deltaH=(0.030molSO2(-296.83 kJ/mol))-(0.030molSO3(-395.72 kJ/mol))

[Shally Li 2C]

Use the stoichiometric coefficients to find reaction enthalpy. So delta H = 2(-395.72)-2(-296.83). Then to find the enthalpy for 0.030 mol, divide your delta H by two and multiply by 0.030.