# chemistry

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9. using bond energies, estimate the change in Hr for the following reaction.

2NO + O2--->2NO2
A 1624 kJ
B -247kJ
C 661 kJ
D 54kJ

10. using bond energies estimate the change Hr for the follwing reaction
C + 1/2O2 +1/2 N--->O=C=N
a -611kJ
b 109kJ
c 2770kJ
d -1090 kJ

Don't you have a table in your text that lists bond energies? If you don't know where it is in the text, look in the index under energy, and then bond under that. There usually is a table for single bonds and another for multiple bonds. Look up the bond energies, then perform the following calculation:
Hrxn=(sum of B.E. for products) - (sum of B.E. for reactants).

If there is a coefficient, as in #1, multiply the B.E. by the coefficient as part of the sum above.
Post your work if you get stuck and need more assistance. Be sure to explain what you don't understand.

Hrxn = (sum of B.E. for reactants) - (sum B. E. for products).

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