Question

@thomaster @amistre64


Use Hess's law and the following equations to calculate ΔH for the reaction SO2(g) + NO2(g) SO3(g) + NO(g). (Show your work.)

SO3(g) SO2(g) + O2(g) ΔH = –98.4 kJ/mol
N2(g) + O2(g) NO(g) ΔH = 90.3 kJ/mol
NO2(g) N2(g) + O2(g) ΔH = –33.1 kJ/mol

Answer 1

you wanna arrange these equations:

(1) SO3(g) <-> SO2(g) + O2(g) ΔH = –98.4 kJ/mol
(2) N2(g) + O2(g) <-> NO(g) ΔH = 90.3 kJ/mol
(3) NO2(g) <-> N2(g) + O2(g) ΔH = –33.1 kJ/mol

i numbered them so i can refer back to them.

so they look like this
SO2(g) + NO2(g) <-> SO3(g) + NO(g).

i'll start, for example, look at equation (1), SO2 is on the wrong side, so reverse it, and reverse the dH sign as well:

(1) SO2(g) + O2(g) <-> SO3(g) ΔH = +98.4 kJ/mol


sounds better?