signs of delta H

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Courtney_Koenig_3K
Posts: 26
Joined: Wed Sep 21, 2016 2:56 pm

signs of delta H

Postby Courtney_Koenig_3K » Thu Feb 02, 2017 7:59 pm

If a question asks how much heat is removed from a system, would the answer always be positive?
I found delta H and it was negative, so I don't know if I keep it as a negative, or make it a positive cause it is asking for how much heat and not the change in heat.

Chem_Mod
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Re: signs of delta H

Postby Chem_Mod » Thu Feb 02, 2017 8:59 pm

Hello Courtney,

First of all, remember that when heat, q, is negative, heat is removed from the system.

It sounds like you did get the sign right, but might have mixed up what it means when q and are negative and positive

Negative: Means exothermic and releasing heat

Positive: Means endothermic and absorbing heat

Courtney_Koenig_3K
Posts: 26
Joined: Wed Sep 21, 2016 2:56 pm

Re: signs of delta H

Postby Courtney_Koenig_3K » Thu Feb 02, 2017 11:21 pm

I know for an exothermic system delta H is negative, but if the question is asking for the quantity of that heat, would the quantity be positive?

For example, if delta H= -1500kJ/mol, would we say that 1500kJ/mol is removed from the system?

Rika Jitosho 2E
Posts: 29
Joined: Fri Jun 17, 2016 11:28 am

Re: signs of delta H

Postby Rika Jitosho 2E » Sun Feb 05, 2017 5:37 pm

Yes, I believe that would be correct! At the end of your calculation you would keep the negative sign since that is the correct numerical value, and then in your answer, you would interpret the negative H value as the amount of heat being released from the system.


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