Delta H and its affect

Moderators: Chem_Mod, Chem_Admin

Ashley Lopez 3J
Posts: 95
Joined: Wed Sep 30, 2020 10:06 pm

Delta H and its affect

Postby Ashley Lopez 3J » Sun Jan 10, 2021 2:37 pm

How do the values of delta H influence the way we determine how there's a shift in equilibrium when there's an increase in temp and vice versa? In other words, what do negative and positive values of delta H mean for the reaction?

Halle Villalobos 3E
Posts: 95
Joined: Wed Sep 30, 2020 9:52 pm

Re: Delta H and its affect

Postby Halle Villalobos 3E » Sun Jan 10, 2021 2:44 pm

Hi! A reaction is exothermic when delta H is negative and is endothermic when delta H is positive. Based on this, you can figure out which direction either a cooling or heating will shift the K. I hope this helps!

Farah Abumeri 3F
Posts: 99
Joined: Wed Sep 30, 2020 9:51 pm
Been upvoted: 2 times

Re: Delta H and its affect

Postby Farah Abumeri 3F » Sun Jan 10, 2021 2:47 pm

A negative delta H means that the reaction is giving off heat, exothermic. A positive delta H means that the reaction requires heat, endothermic. I think Dr. Lavelle has mentioned that the enthalpy, H, of the reactants and products is going to become significant in future lectures in determining the stability of the reactants and products. For now, I think we have to understand that heating an endothermic reaction favors the products (which have a greater enthalpy relative to the reactants), and heating an exothermic reaction favors the reactants (which have a greater enthalpy relative to the products).

Bella Wachter 1A
Posts: 95
Joined: Wed Nov 18, 2020 12:17 am
Been upvoted: 2 times

Re: Delta H and its affect

Postby Bella Wachter 1A » Sun Jan 10, 2021 2:49 pm

A negative value of delta H indicates that the reaction is exothermic. An exothermic reaction releases heat in the forward direction, so the "heat" lies on the right side of the equation. If temperature increases, an exothermic reaction will shift left, and if the temperature decreases, an exothermic reaction will shift right.

A positive value of delta H indicates that the reaction is endothermic. An endothermic reaction absorbs/requires heat in the forward direction, so the "heat" lies on the left side of the equation. If the temperature increases, an endothermic reaction will shift right, and if the temperature decreases, an endothermic reaction will shift left.

Hope this helps!!

Pranav Daggubati 3C
Posts: 118
Joined: Wed Sep 30, 2020 9:35 pm

Re: Delta H and its affect

Postby Pranav Daggubati 3C » Sun Jan 10, 2021 3:17 pm

H is enthalpy. A positive delta H means that enthalpy is increasing due to increase in energy (endothermic) and the opposite is doe to a decrease (exothermic) in the system. Energy is drawn from bond rearrangement and from the environment.

Anna Lockhart 2B
Posts: 45
Joined: Tue Nov 17, 2020 12:19 am

Re: Delta H and its affect

Postby Anna Lockhart 2B » Sun Jan 10, 2021 3:46 pm

I am not sure if this has been taught yet, but how do we determine if a reaction is endo/exothermic?


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