Hess's Law

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Blake_Katsev_2E
Posts: 113
Joined: Wed Sep 21, 2016 2:57 pm

Hess's Law

Postby Blake_Katsev_2E » Mon Jan 16, 2017 12:26 am

How do you know when to flip an equation or halve or double it?
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Armo_Derbarsegian_3K
Posts: 35
Joined: Sat Jul 09, 2016 3:00 am

Re: Hess's Law

Postby Armo_Derbarsegian_3K » Mon Jan 16, 2017 1:11 am

When you need to cancel things from both sides. You switch signs to flip it.

for example:

A+B->C dH=x
2C->2A+D dH=y

you would multiply the top one by 2 to get A and C to cancel.
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gohar_mkrtchyan_2J
Posts: 12
Joined: Sat Jul 09, 2016 3:00 am

Re: Hess's Law

Postby gohar_mkrtchyan_2J » Mon Jan 16, 2017 1:24 am

you should also know that when you reverse an equation, you have to reverse the sign on the enthalpy value too.
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Cobie_Allen_1H
Posts: 24
Joined: Wed Sep 21, 2016 2:56 pm

Re: Hess's Law

Postby Cobie_Allen_1H » Mon Jan 16, 2017 12:56 pm

I still don't really get when we should flip the reaction? Could you explain that for me?

Thanks!
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