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March 27, 2015

March 27, 2015

Posted by **anna** on Saturday, March 26, 2011 at 9:13pm.

I can't figure out how to start this one. I know I need to figure out hte proportions or something of that sort. Any help is greatly appreciated Thanks!

Calculate H for the reaction

NO(g) + O(g) NO2(g)

given the following:

NO(g) + O3(g) NO2(g) + O2(g)

H = -198.9 kJ

O3(g) 3/2 O2(g)

H = -142.3 kJ

O2(g) 2O(g)

H = 495.0 kJ

- chemistry -
**DrBob222**, Saturday, March 26, 2011 at 9:37pmI assume those strange symbols stand for delta H.

Write equation 1 as is.

Reverse equation 2 and add to 1.

Take 1/2 of equation 3 and reverse it; add to the other two.

When you reverse an equation you change the sign of delta H. If you take 1/2 of an equation you take 1/2 delta H.

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