## Exothermic vs. Endothermic Reaction

Kathryn Wilhem 1I
Posts: 60
Joined: Fri Sep 28, 2018 12:27 am

### Exothermic vs. Endothermic Reaction

How do we know if a reaction is endothermic or exothermic? Can we only know if we are given delta H?

rachana_korapati3C
Posts: 39
Joined: Fri Sep 28, 2018 12:25 am

### Re: Exothermic vs. Endothermic Reaction

I don't think you can tell whether a reaction is exothermic or endothermic by the equation alone. You have to either measure the heating to cooling or know enough about similar types of reactions.

Nathan Tran 4K
Posts: 92
Joined: Fri Sep 28, 2018 12:16 am

### Re: Exothermic vs. Endothermic Reaction

I know the triangle on top of the arrow indicates there is heat involved, so you know that equation can be endothermic or exothermic. However, to determine whether a reaction is exothermic or endothermic, I would assume we would be given delta H or some variation of it.

juliasloan_4g
Posts: 67
Joined: Fri Sep 28, 2018 12:28 am

### Re: Exothermic vs. Endothermic Reaction

Yes you should be given delta h in order to determine whether the action is endo( taking in heat) or exo(giving off heat)thermic

jonathanjchang2E
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

### Re: Exothermic vs. Endothermic Reaction

You can predict if a reaction is endothermic or exothermic by looking at the energies of the reactants and products (but this way is really hard with more complicated reactions). For example if you're given H2 = 2H, it would probably be endothermic since H2 is lower in energy than 2 H.

shaunajava2e
Posts: 66
Joined: Fri Sep 28, 2018 12:26 am

### Re: Exothermic vs. Endothermic Reaction

A quick difference between endothermic and exothermic involves reactions in the environment. An endothermic reaction takes place when energy is absorbed from surroundings in the form of heat, and exothermic is when energy is released from the system into the surroundings.

Samantha Chang 2K
Posts: 69
Joined: Fri Sep 28, 2018 12:17 am

### Re: Exothermic vs. Endothermic Reaction

We can know if a reaction is endothermic when heat is absorb and in contrast an exothermic reaction is when heat is released. This is how one can environmentally tell if a reaction is exothermic and endothermic. Other than that, I think one has to know if delta H is negative or positive.

Melissa Bu 1B
Posts: 36
Joined: Fri Sep 28, 2018 12:19 am

### Re: Exothermic vs. Endothermic Reaction

It helps to see an energy graph to think about why exothermic has a negative change in H and endothermic has a positive change in H. In exothermic reactions, heat is leaving the system, so the graph will end up at a lower delta H value in the products compared to the reactants. Therefore, the change in H will be negative (smaller H - larger H < 0). In endothermic reactions, heat is being put into the system/the system absorbs hear, so the graph will end up at a higher delta H value in the products compared to the reactants. Therefore, the change in H will be positive (larger H - smaller H > 0).

Cynthia Aragon 1B
Posts: 47
Joined: Mon Apr 09, 2018 1:38 pm

### Re: Exothermic vs. Endothermic Reaction

An endothermic reaction absorbs energy from the surrounding and exothermic reaction releases/ produces heat.
Endothermic: delta H >0
Exothermic: delta H < 0

Nicolle Fernandez 1E
Posts: 56
Joined: Fri Sep 28, 2018 12:25 am
Been upvoted: 1 time

### Re: Exothermic vs. Endothermic Reaction

When a reaction gives off heat it is exothermic, but when a reaction requires heat it is endothermic. SO for a reaction the be exothermic the change in H must be less than than 0. For a reaction to be endothermic the change in H is greater than 0.

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