Page 1 of 1

### Endothermic and exothermic reactions

Posted: Tue Jan 14, 2020 6:01 pm
Can someone explain why endothermic reactions favor product formation while exothermic reactions favor reactant formation? I don't understand how the graphs and delta H relate to the concept when explaining product/reactant formation.

### Re: Endothermic and exothermic reactions

Posted: Tue Jan 14, 2020 6:21 pm
Endothermic reactions favor product formation if the temperature increases and vice versa. Exothermic reactions favor reactant formation if temperture increase. The opposite is true if temperture decreases. Equations tend to resist change by doing the opposite of what is happening around them

### Re: Endothermic and exothermic reactions

Posted: Tue Jan 14, 2020 8:12 pm
Also, the way I think about it is that endothermic reactions like heat because they absorb it, so more heat will help the reaction favor the products. If the reaction is exothermic, it "doesn't like heat" so it lets it go, and wouldn't want to create more products if the temperature rises.

### Re: Endothermic and exothermic reactions

Posted: Tue Jan 14, 2020 8:19 pm
I've heard someone explain it like this before: think of heat as either another reactant or product. If the reaction is endothermic, the system absorbs heat and heat is considered a reactant. Say you heat up the system, you're adding heat (a "reactant"), which means the reaction will favor product formation. And vice versa with exothermic reactions.

### Re: Endothermic and exothermic reactions

Posted: Tue Jan 14, 2020 8:49 pm
Alexis Webb 2B wrote:Also, the way I think about it is that endothermic reactions like heat because they absorb it, so more heat will help the reaction favor the products. If the reaction is exothermic, it "doesn't like heat" so it lets it go, and wouldn't want to create more products if the temperature rises.

I'm a little confused though because if the product had a solid in it then wouldn't the forward reaction be exothermic, and the reverse endothermic? I feel as if the example Lavelle gave was theoretical. Generally the forward and reverse reactions would be opposite of each other is what I thought Lavelle was trying to get across. So if the forward reaction is endothermic then the reverse must be exothermic and vice a versa. Can anyone help here?

### Re: Endothermic and exothermic reactions

Posted: Wed Jan 15, 2020 5:02 pm
If the temperature increases, the reaction will favor the products in an endothermic reaction because it requires heat to form the product. If you add heat, the reaction is going to want to use up that heat. Therefore, in an endothermic reaction, the reaction will continue forward, towards the product. The exothermic reaction uses the same concept. An exothermic reaction will release heat in order to form the product, which means that it would require heat to form the reactant again. So, when you add heat to an exothermic reaction, the reaction will go in the reverse direction, towards the reactant.

### Re: Endothermic and exothermic reactions

Posted: Wed Jan 15, 2020 5:13 pm
Endothermic processes require an input of energy to proceed and are signified by a positive change in enthalpy. Overall an increase in temp will love the forward reaction favoring the products. Exothermic processes release energy upon completion, and are signified by a negative change in enthalpy, performing the opposite of a endothermic reactions (favoring reverse as in the reactants)

### Re: Endothermic and exothermic reactions

Posted: Wed Jan 15, 2020 5:33 pm
What helps me visualize this is to treat the energy almost like a product or reactant. So if the reaction is exothermic, energy is a "product" and vice versa. If you increase the temp, you would increase the delta H, so whichever side it is on will end up decreasing.

### Re: Endothermic and exothermic reactions

Posted: Thu Jan 16, 2020 4:49 pm
Bilal Pandit 1J wrote:What helps me visualize this is to treat the energy almost like a product or reactant. So if the reaction is exothermic, energy is a "product" and vice versa. If you increase the temp, you would increase the delta H, so whichever side it is on will end up decreasing.

This is helpful, but would that mean that if the reaction is endothermic you treat the energy as a reactant?

### Re: Endothermic and exothermic reactions

Posted: Fri Jan 17, 2020 3:57 pm
Yes, some chemical equations will include delta H, or heat in the reaction to show if heat is absorbed or released in the reaction.

### Re: Endothermic and exothermic reactions

Posted: Fri Jan 17, 2020 4:01 pm
This might help

### Re: Endothermic and exothermic reactions

Posted: Fri Jan 17, 2020 4:06 pm
Because as you can see in the graph the energy of the products is higher than that of the reactants in an endothermic reaction than you know that you require heat to go to this higher energy state. On the other hand, in an exothermic reaction, you are going from a higher energy state to a lower energy state so as a result, the system releases energy.