## Delta H

Jessica Castellanos
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Joined: Sat Aug 24, 2019 12:17 am
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### Delta H

When delta H is positive, is it endothermic or exothermic? And if H is negative?

Kevin Antony 2B
Posts: 99
Joined: Sat Sep 07, 2019 12:16 am

### Re: Delta H

To see if something is endothermic r exothermic we look at delta G. If delta G is positive, the reaction is endothermic, but if it is negative the reaction is exothermic.

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

### Re: Delta H

Jessica Castellanos wrote:When delta H is positive, is it endothermic or exothermic? And if H is negative?

If delta H is positive, that means the sum of the enthalpy of reactants is LARGER than the sum of the enthalpy of products. This means that the reaction is endothermic, or uses heat.

If delta H is negative, the sum of the enthalpy of reactants is SMALLER than the sum of the enthalpy of products. This means that the reaction is exothermic, or releases heat. Dr. Lavelle said that we will go more in depth about delta H, delta G and delta S later in the quarter.

Hussain Chharawalla 1G
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Joined: Sat Jul 20, 2019 12:15 am

### Re: Delta H

If it helps, another way to think of delta H or enthalpy is the energy stored in bonds. If the products are in a lower energy more stable configuration, the reaction will be exothermic.

aishwarya_atmakuri
Posts: 101
Joined: Sat Jul 20, 2019 12:15 am

### Re: Delta H

If delta H is negative, it is exothermic. If delta H is positive, it is endothermic.

Ashley Fang 2G
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Joined: Fri Aug 30, 2019 12:17 am

### Re: Delta H

sarahforman_Dis2I wrote:
Jessica Castellanos wrote:When delta H is positive, is it endothermic or exothermic? And if H is negative?

If delta H is positive, that means the sum of the enthalpy of reactants is LARGER than the sum of the enthalpy of products. This means that the reaction is endothermic, or uses heat.

If delta H is negative, the sum of the enthalpy of reactants is SMALLER than the sum of the enthalpy of products. This means that the reaction is exothermic, or releases heat. Dr. Lavelle said that we will go more in depth about delta H, delta G and delta S later in the quarter.

I believe you switched it the other way, the idea is enthalpy of products - enthalpy of reactants = delta H
But yes, positive delta H means endothermic, negative delta H means exothermic.

Caroline Beecher 2H
Posts: 51
Joined: Wed Nov 14, 2018 12:21 am

### Re: Delta H

The rule of thumb is that when delta H is positive, it is endothermic (it takes up heat and its' surroundings become cooler) and when delta H is negative, it is exothermic (it releases heat and its' surroundings become warmer).

Jialun Chen 4F
Posts: 108
Joined: Sat Sep 07, 2019 12:16 am

### Re: Delta H

I agree with Caroline's answer. If positive Delta H, endothermic; if negative Delta H, exothermic.

Sean Cheah 1E
Posts: 105
Joined: Wed Sep 18, 2019 12:20 am

### Re: Delta H

Kevin Antony 2B wrote:To see if something is endothermic r exothermic we look at delta G. If delta G is positive, the reaction is endothermic, but if it is negative the reaction is exothermic.

When determining whether a reaction is exothermic/endothermic, one should look at the sign of delta H (change in enthalpy). The sign of G tells you whether a given reaction is exergonic/endergonic, which sounds similar but is completely different.

Michellekim1H
Posts: 25
Joined: Wed Feb 20, 2019 12:17 am

### Re: Delta H

Positive delta H is endothermic(since there’s more energy in the products) whereas negative delta H is exothermic(there’s less energy in the products).

Elizabeth Harty 1A
Posts: 125
Joined: Sat Jul 20, 2019 12:16 am

### Re: Delta H

positive delta H means endothermic, negative delta H means exothermic.

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