THERMOCHEMISTRY TRICK PROBLEM-SOLVING HELP FAVE ANS!?

Question

Please explain this, I am clueless. I hope I can be given some direction and understanding about the step-by-step process.

hcbiochem · Answer

1. Use the coefficients in the balanced reaction:
-126 kJ/4 mol NaOH X 2 mol NaOH = -63 kJ

2. Leave the first reaction as it is:
N2H4(l) + O2 --> N2(g) + 2 H2O(l) Delta H = -622.3

Flip the third equation over and multiply it by 2:
2 H2O2(l) --> 2 H2 + 2 O2 Delta H = +375.6

Multiply the middle equation by 2:
2 H2 + O2 --> 2 H2O Delta H = -571.6 kJ

Add the three equations (and their delta H values) and simplify to give you the desired equation. Its Delta H = -818.3 kJ