Question

Which formulas should I use to calculate the heat of a reaction?

Answer 1

Heat of formation of products - heat of formation of starting compounds.
Remember also multiply by number of moles

Answer 2

How do I find the heats? I see 2NO will be 2(90.4), but I do not see what O2 is.

Answer 3

For elements, like O2, Na, N2, C,.. Value is zero

Answer 4

I see. So am I right to say problem a) is 33.9-180.8?

Answer 5

Multiply also 33.9 by two. There is2 molecules.

Energy is negative, because burning reaction is exothermic