# Hess' Laws

1. Nov 21, 2005

### Soaring Crane

Given the following information:
Fe2O3 + 3CO -> 2Fe + 3CO2 Heat = -28.0 kJ
3Fe + 4CO2 -> 4 CO + Fe3O4 Heat =-12.5 kJ
FInd the heat for the following reaction:
Fe2O3 + CO -> CO2 + Fe3O4
Balance the equation first and remember to include the correct units.

3Fe2O3 + CO -> CO2 + 2Fe3O4

Fe2O3 + 3CO --> 2Fe + 3CO2 H = -28 kJ
2(3Fe + 4CO2 --> 4CO + Fe3O4 H = -12.5 kJ)

3(Fe2O3 + 3CO --> 2Fe + 3CO2 H = -28.0 kJ)
6Fe + 8CO2 --> + 2 Fe3O4 H = -25.0 kJ

3Fe2O3 + 9CO --> 6Fe + 9CO2 H = -84.0
6Fe + 8CO2 --> 8CO + 2Fe3O4 H = -25.0 kJ

Thus, 3Fe2O3 + CO -> CO2 + 2Fe3O4 and H = -109 kJ??

Use the presented information to find the  H for: N2 + O2 ->2NO
1/2 N2 + O2 -> NO2 H = 32.16
4NO + 2O2 ->4NO2 H = -227.9

1/2 N2 + O2 -> NO2 H = 32.16
1/2 (4NO + 2O2 ->4NO2 H = -227.9)

2(1/2 N2 + O2 -> NO2 H = 32.16)
2NO2 --> 2NO + O2 H = +113.95

N2 + 2O2 --> 2NO2 H = 64.32
2NO2 --> 2NO + O2 H = +113.95

Thus, N2 + O2 ->2NO and H = 178.27 = 178.3 ?? I suppose the units are kJ even if they didn't state which units are used?

Thanks.

2. Nov 22, 2005

### Soaring Crane

Any volunteers?

Thanks again.

3. Nov 22, 2005