Endothermic vs exothermic

Moderators: Chem_Mod, Chem_Admin

504939134
Posts: 103
Joined: Wed Sep 18, 2019 12:21 am

Endothermic vs exothermic

Postby 504939134 » Thu Jan 16, 2020 9:20 pm

Can someone please explain why :
1. If a reaction requires Heat, (is endothermic) while forming products, then heating will favor P (product) formation when additional heat is used.
2. If a reaction gives off heat, (is exothermic) while forming products, then heating will favor R formation when additional heat is used.

Thank you.

Connie Chen 1E
Posts: 51
Joined: Mon Jun 17, 2019 7:24 am

Re: Endothermic vs exothermic

Postby Connie Chen 1E » Thu Jan 16, 2020 9:53 pm

For endothermic reactions, since there is more heat, it will be easier to overcome the activation energy, thus making it easier to form more products. As a result, the products will be favored.
For exothermic reactions, the reverse reaction (P-->R) will be endothermic. So using the logic that the reverse reaction is endothermic, there will be more reactants formed, as it is the products of the reverse reaction.

DLee_1L
Posts: 103
Joined: Sat Aug 17, 2019 12:17 am

Re: Endothermic vs exothermic

Postby DLee_1L » Fri Jan 17, 2020 9:35 am

If it helps, I always look at heat as if it is another substance in the chemical equation when given a le Chatlier question. This makes it easier to see whether a heat increase or decrease will lead to a shift to products or reactants

William Francis 2E
Posts: 101
Joined: Wed Sep 18, 2019 12:20 am

Re: Endothermic vs exothermic

Postby William Francis 2E » Fri Jan 17, 2020 10:43 am

Endothermic reactions are hungry for heat. You can think of heat as a reactant in the equation necessary for the reaction to run: AB + heat <--> A + B. Therefore, when the reaction gets heat, it favors the forward reaction, resulting in a raised concentration of the products. The opposite is true for exothermic reactions; heat is a reactant for the reverse reaction so the reactants are favored when heat is added.

Alice Chang 2H
Posts: 101
Joined: Fri Aug 30, 2019 12:18 am

Re: Endothermic vs exothermic

Postby Alice Chang 2H » Sat Jan 18, 2020 3:40 pm

If you're more of a visual learner, Khan Academy has a video explaining Le Chatelier's Principle here: https://www.khanacademy.org/science/chemistry/chemical-equilibrium/factors-that-affect-chemical-equilibrium/v/le-chatelier-s-principle


Return to “Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions”

Who is online

Users browsing this forum: No registered users and 1 guest