positive vs. negative delta H

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005199302
Posts: 108
Joined: Fri Sep 28, 2018 12:15 am

positive vs. negative delta H

Postby 005199302 » Tue Jan 15, 2019 1:49 pm

Is it true that when delta H is positive it's endothermic and if delta H is negative it's exothermic? If so, why is that?

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

Re: positive vs. negative delta H

Postby A De Castro 14B 2H » Tue Jan 15, 2019 1:53 pm

Positive delta H is endothermic because the system absorbed heat, which means that there is more energy in the products side. This results to a positive difference in H, when H of reactants is subtracted from H of products. On the other hand, negative delta H is exothermic because the system released heat, meaning there is more energy in the reactants side. When H of reactants is subtracted from H of products, it would result in a negative difference in H values.

Tam To 1B
Posts: 72
Joined: Fri Sep 28, 2018 12:25 am

Re: positive vs. negative delta H

Postby Tam To 1B » Tue Jan 15, 2019 1:54 pm

Delta H basically means the change in enthalpy, or in other words, the change in "heat".
When delta H is positive, it means the products in the reaction have more energy compared to the reactants, so the reaction has gained energy, making it endothermic.
When delta H is negative, it means the products in the reaction have lower energy compared to the reactants, so the reaction has lost energy and released it as heat, making it exothermic.
You can think of it as positive delta H as gaining energy and negative delta H as releasing energy.


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