[GenAp]

Just trying to calculate an enthalpy practice problem.

NO+O₃   NO₂ + O₂ -198.9kJ

O₃   3/2 O₂ -142.3 kJ

O₂   2 O 495.0 kJ

The provided answer is -304.1 kJ

The end-result equation (if that's the right way to put it) is  NO + O NO₂

I've tried putting co-efficients of 2 on the first two equations, in addition to switching the 2nd around, but no matter what I do, I simply can't get the desired answer. :/ I continually get tripped up by the 2 O in the last equation; could that cancel with an O₂, or are they two separate things entirely? If anyone could provide me with the correct co-efficients and kJ levels, I'd be very grateful.

[UG]

Your final equation has 1 O on the left hand side, and the only equation containing O is the third equation, which has O on the right hand side, so you will need to rearrange this and change the coefficients. You then need to cancel out the O₂ and O₃ species by rearranging the second equation.

[GenAp]

Thanks bud! C: Helped out a lot!