Le chatelier and Temperature

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Matt Sanruk 2H
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Le chatelier and Temperature

Postby Matt Sanruk 2H » Wed Jan 22, 2020 11:47 pm

I know this depends on the delta H, but what happens if the temperature is changed? For example: delta H is positive and temperature is increased, what would happen?

Jordan Young 2J
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Re: Le chatelier and Temperature

Postby Jordan Young 2J » Wed Jan 22, 2020 11:49 pm

If delta H is positive (endothermic) and temperature is increased, then the reaction would proceed towards the products. If delta H is negative (exothermic), then the reaction would proceed towards the reactants if temperature is increased.

Matt Sanruk 2H
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Re: Le chatelier and Temperature

Postby Matt Sanruk 2H » Wed Jan 22, 2020 11:50 pm

Oh so it would be treated as if you added products or reactants depending on the sign of delta H

Hope Hyland 2D
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Re: Le chatelier and Temperature

Postby Hope Hyland 2D » Thu Jan 23, 2020 12:15 am

if delta h is positive for a reaction (aka endothermic, or requires heat), and you increase the temperature, then the reaction will favor the formation of products since the heat is used to make products. As a result, K will increase for endothermic reactions when the temperature is increased. On the other hand, if delta h is negative for a reaction (exothermic, or releases heat), then the reaction will favor the formation of reactants and K will decrease.

LNgo 1G
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Re: Le chatelier and Temperature

Postby LNgo 1G » Thu Jan 23, 2020 9:29 am

When a reaction is endothermic, it requires heat and has a positive delta H value, so you can think of heat as a reactant in a way. When it is exothermic, heat is given off during the reaction and delta H is negative, so heat can be thought of as a product of the reaction in this case.

Celine 1F
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Re: Le chatelier and Temperature

Postby Celine 1F » Thu Jan 23, 2020 10:16 am

If delta H is positive and heat is added, then the equilibrium will shift to the products side. If delta H is negative and heat is added, then equilibrium will shift to the reactants

Nathan Nakaguchi 1G
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Re: Le chatelier and Temperature

Postby Nathan Nakaguchi 1G » Thu Jan 23, 2020 11:29 am

For Delta H= +, then the reaction is endothermic meaning it needs input

For Delta H= -, then the reaction is exothermic and is spontaneous/needs no input.

The way I like to think about these is that for endothermic reactions, they are going from generally a more stable form to a less stable form thus they need energy/heat from their surroundings to reach the product state. For exothermic reactions, they are going from a less stable to more stable form so it is more favorable when there isn't much heat energy to give.

For example, if there is a endothermic reaction and the temperature increases, you are giving the system more energy/heat to be able to move towards the less stable form (i.e.products)

If there is an exothermic reaction and the temperature increases, there is more energy present for the less stable side to form so it will move towards reactants.

Hope this helps!

Abby Soriano 1J
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Re: Le chatelier and Temperature

Postby Abby Soriano 1J » Thu Jan 23, 2020 12:12 pm

If delta H is positive, the reaction is endothermic and takes in heat on the reactant side. Therefore, if the temperature were to increase, there would be more heat coming in on the left, forcing the reaction to favor the right (the product side) to balance itself out again.

Nicholas_Gladkov_2J
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Re: Le chatelier and Temperature

Postby Nicholas_Gladkov_2J » Thu Jan 23, 2020 12:29 pm

Matt Sanruk 2H wrote:I know this depends on the delta H, but what happens if the temperature is changed? For example: delta H is positive and temperature is increased, what would happen?


Delta H helps you determine if the reaction is exothermic or endothermic. If the reaction is endothermic, then heat is needed and is a reactant (delta H is positive). If the reaction is exothermic, then heat is given off as a product (delta H is negative). In the example you gave, delta H is positive, and therefore, the reaction is endothermic. If the temperature is increased, then more reactant is added, and thus the reaction will favor products.

Celena Kim 2I
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Re: Le chatelier and Temperature

Postby Celena Kim 2I » Thu Jan 23, 2020 4:18 pm

If temperature is increasing and delta h is positive, reaction will shift towards products. This is also true if temperature is decreasing and delta h is negative.
If temperature is increasing and delta h is negative, reaction will shift towards reactants. This is also true if temperature is decreasing and delta h is positive.


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