# Chemistry

Calculate the enthalpy change for the reaction 2C + H2 yield C2H2 given the following reactions and their respective enthalpy changes:

C2H2 + 5/2 O2 yield 2CO + H2O -1299.6
C + O yield CO2 -393.5
H2 + 1/2 O2 yield H2O -285.9

I don't even know how to start and the example in the book doesn't explain anything!!!!

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asked by Lucy
1. Look in your text about Hess' Law. That is what this problem is. The idea is to multiply (if necessary) an equation AND/OR reverse it so that all of them added together will give you the final equation you want.
If you get stuck let us know what you don't understand (be specific---; i.e., I don't know where to start or I don't have a clue doesn't help us determine the problem you are having.)

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2. Check you post carefully. I don't think all of the equations you have written are balanced. For example, look at the ones with CO. Are those CO2?

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