Endothermic/exothermic reactions and K

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Melody Haratian 2J
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Endothermic/exothermic reactions and K

Postby Melody Haratian 2J » Sun Jan 17, 2021 9:58 am

For endothermic reactions, how does K change when you add heat. How does K change when you add heat to exothermic reactions? Also, why does K change instead of Q when you add heat to the reaction.

Kyla Roche 2K
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Re: Endothermic/exothermic reactions and K

Postby Kyla Roche 2K » Sun Jan 17, 2021 10:19 am

K changes because temperature changes the equilibrium constant itself. For an endothermic reaction, which means a positive delta H, K becomes bigger because the production of products is favored so the numerator of the K ratio is bigger when heated.On the other hand, for an exothermic reaction where delta H is negative, K becomes smaller because heating it will favor reactant production. By cooling it, products are favored thus K becomes bigger.

Megan Lu 3D
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Re: Endothermic/exothermic reactions and K

Postby Megan Lu 3D » Sun Jan 17, 2021 11:21 am

Hi! For exothermic reactions, heat is released for the forward reaction; thus, the addition of heat would favor the reverse reaction instead to produce more reactants, and the K value would decrease. For endothermic reactions, heat is absorbed for the forward reaction; thus, the addition of heat would favor the forward reaction to produce more products, and the K value would increase. Hope this helps!

Evelyn Silva 3J
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Re: Endothermic/exothermic reactions and K

Postby Evelyn Silva 3J » Sun Jan 17, 2021 11:46 am

When there is an endothermic reaction, you can think of heat as a reactant. Increasing the temperature makes K increase because the equilibrium favors more products and less reactants. We know that K=[P]/[R], so if your denominator is smaller then the value of K will be bigger. In an exothermic reaction, you can think of heat as a product. Increasing the temperature makes K decrease because the equilibrium favors more reactants and less products. This means that in your equilibrium constant (K=[P]/[R]) the denominator will be bigger and therefore make K decrease.

Shreyank Kadadi 3K
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Re: Endothermic/exothermic reactions and K

Postby Shreyank Kadadi 3K » Sun Jan 17, 2021 12:17 pm

I like to think about it as what each reaction "wants":

Endothermic reactions "want" heat so an increase in temperature favors the forward reaction and increases the value of K (and vice versa).
Exothermic reactions do not "want" heat, so an increase in temperature favors the reverse reaction and decreases the value of K (and vice versa).

JonathanM
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Re: Endothermic/exothermic reactions and K

Postby JonathanM » Sun Jan 17, 2021 4:09 pm

Hey!
So exothermic reactions release heat when turning into products, so when you add more heat to the system, products will tend to form reactants more often, the equilibrium will shift to favor the reactants more. Since K is equivalent to the products raised to their stoichiometric coefficients, over the reactants to their stoichiometric coefficients, K will decrease as the reaction shifts to the reactants. The inverse is true of endothermic reactions. Heat is taken up when forming products, so adding heat will favor the products, causing K to increase. And K changes because the actual ratio of products and reactants changes when temperature changes, whereas Q just describes the state of the system, so if k changes, Q will also start to change to reach equilibrium again.

Sophia Kalanski 1A
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Re: Endothermic/exothermic reactions and K

Postby Sophia Kalanski 1A » Sun Jan 17, 2021 4:15 pm

Hi! So K will change because the change in temperature has an affect on the equilibrium constant. If the delta H is positive (endothermic reaction) and heat is added, it will cause K to increase because it will favor products being made since an increase in heat will favor the forward reaction. If delta H is negative (exothermic) and heat is added, it will favor the reactants and K will decrease

Jaden Joodi 3J
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Re: Endothermic/exothermic reactions and K

Postby Jaden Joodi 3J » Sun Jan 17, 2021 4:29 pm

For endothermic reactions, K increases when temperature increases
For exothermic reactions, K decreases when temperature increases.

Kiana Tashakori 1D
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Re: Endothermic/exothermic reactions and K

Postby Kiana Tashakori 1D » Sun Jan 17, 2021 4:37 pm

Hi! K changes when you add heat to a reaction because the equilibrium constant changes. More reactants will be produced, so reactants would be favored. K will increase as the temperature increases in endothermic reactions, and it will decrease when temperature increases in an exothermic reaction.

Lauren Sarigumba 1K
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Re: Endothermic/exothermic reactions and K

Postby Lauren Sarigumba 1K » Sun Jan 17, 2021 4:47 pm

A change in temperature changes the equilibrium constant K. When increasing the heat and the reaction is endothermic, K will increase. When increasing the heat and the reaction is exothermic, K will decrease.

David Y
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Re: Endothermic/exothermic reactions and K

Postby David Y » Sun Jan 17, 2021 5:06 pm

For endothermic reaction, temperature increases with K.

Justin Zhang_1A
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Re: Endothermic/exothermic reactions and K

Postby Justin Zhang_1A » Sun Jan 17, 2021 5:46 pm

If a reaction is endothermic and temperature is increased, K will increase. If the reaction is exothermic and temperature is increased, then K will decrease.


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