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September 19, 2014

September 19, 2014

Posted by **Anonymous** on Thursday, April 8, 2010 at 3:26pm.

2H2 + O2 - 2H2O delta H = -571.6 kJ

N2O5 + H2O - 2HNO3 deltaH = -73.7 kJ

1/2N2 + 3/2O2 + 1/2H2 - HNO3 delta H = -174.1 kJ

- Chem -
**DrBob222**, Thursday, April 8, 2010 at 4:13pmI believe you need to do the following:

reverse equation 1 and change sign of delta H.

Multiply equation 2 x 2 and reverse. Multiply delta H by 2 and change sign.

Multiply equation 3 by 4. Multiply delta H by 4.

Add the equations and add the delta Hs.

When you finish you should have

2N2 + 5O2 ==> 2N2O5 which is just twice what you are looking for so divide the coefficients by 2 throughout and divide total delta H by 2.

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