Heat Enthalpy Question?

Question

How much energy is released or consumed if 16.0g N2O5 of is completely decomposed as described?

Equation: 2N2O5 -> 4NO2 + O2

So this is what I have so far..

13.3kj/mol = N2O5
33.2kj/mol = NO3
0 kj/mol = O2

Then total h = 4(33.2kj/mol) - 2(13.3kj/mol) = 39.8kj/mol

What do I do now?

Answer 1

First, 4(33.2kJ/mol) - 2(13.3kJ/mol) = 106.2 kJ

That's for decomposition of two moles N2O5 in the equation.

Atomic weights: N=14 O=16 N2O5=108

16.0gN2O5 x 1molN2O5/108gN2O5 x 106.2kJ/2molN2O5 = 7.86kJ consumed

The heat is consumed, because the sign of the answer is (+).