# Chemistry

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HELP!!
I cannot find the value of ÄH, for the following reactions.

A + 2B --> C + 3D , ÄH = 154 kJ

1/2C + 3/2D --> 1/2A + B, ÄH= ?

I have tried the answers -302 and 154 and neither were correct.

Have any suggestions?? Thank You!

• Chemistry -

Isnt the second reaction the first reaction backwards, or 1/2 of it backwards, so deltaH=-154/2 kJ

• Chemistry -

Yes, the 2nd reaction is the 1st reaction reversed.

The book says when you have a reaction that is reversed, take the opposite sign of the ÄH... which should be -154 by that definition. I'm not sure if I am suppose to divide 154 by 2??

• Chemistry -

yes, you are supposed to divide. It is 1/2 of the first reaction backwards.

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