Outline 1, last bullet

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Lina Petrossian 1D
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Joined: Fri Oct 05, 2018 12:16 am

Outline 1, last bullet

Postby Lina Petrossian 1D » Tue Jan 22, 2019 5:12 pm

"Use Le Chatelier's principle to predict how the equilibrium composition of a reaction mixture is
affected by: adding or removing reagents; compressing or expanding a gaseous mixture; and
by raising or lowering the temperature."

Can someone pls give a summary of this?

ThomasLai1D
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Outline 1, last bullet

Postby ThomasLai1D » Tue Jan 22, 2019 5:55 pm

-Adding reagents, Q will become smaller than K, causing more product to be created to compensate and increase Q such that Q=K at equilibrium
-Removing reagent, Q will become large than K, causing reaction to favor reactants to compensate and decrease Q such that Q=K at equilibrium
-Compressing gas mixture increases concentration, so Q will increase towards the side to with the greater number of moles, causing reaction to compensate and adjust towards the opposite side such that Q=K.
-Expanding gas mixture decreases concentration, so Q will decrease towards the side with the greater number of moles, causing the reaction to compensate and adjust towards the opposite side such that Q=K
-Raising temperature favors the products in an endothermic reaction by increasing energy of collisions and thus increasing K
-Decreasing temperature favors the reactants in an endothermic reaction by decreasing K
-In exothermic reaction increase in temperature leads to more reactants and decrease in temperature leads to more products.

Hai-Lin Yeh 1J
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Joined: Fri Sep 28, 2018 12:16 am
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Re: Outline 1, last bullet

Postby Hai-Lin Yeh 1J » Tue Jan 22, 2019 6:02 pm

Le Chatelier's Principle states: chemical reactions adjust so as to minimize the effect of any changes.

Adding or Removing Reagents: [CONCENTRATION]
-Adding reactants: there is more reactants than products so in order to reach equilibrium again, the reaction will proceed towards the right and more products will be produced. The system is responding, trying to minimize the effect of increasing reactants, which is to produce more product.
-Adding products: now there is more products than reactants so in order to reach equilibrium again, the reaction will proceed towards the left and more reactants will be produced. The system is responding, trying to minimize the effect of increasing products, which is to produce more reactants.
-Removing reactants: If you remove some reactants, there is a lack of reactants and too much product is present now. So to reach equilibrium, the reaction will proceed left and produce more reactants to make up for that loss.
-Removing products: If you remove some products, there is a lack of products and too much reactant is present. So to reach equilibrium, the reaction will proceed right and produce more products to make up for that loss.

Compressing or expanding a gaseous mixture: [PRESSURE]
The quick way that Professor Lavelle told us is:
-If volume decreases and there are more moles of gas on the right, then reaction shifts left.
-If volume decreases and there are more moles of gas on the left, then reaction proceeds right.
-If pressure of reaction vessel is increased by adding inert gas, then moles of reactant, product, and volume are constant so there is no change in the system, meaning no effect on reaction.

Raising or Lowering the Temperature: [TEMPERATURE]
-If the reaction requires heat (endothermic) while forming product or in the forward direction, then heating will produce more products. Cooling will produce more reactants and favor the reverse direction.
-If the reaction gives off heat (exothermic) while forming product or in the forward direction, then cooling will produce more products and heating will produce more reactants and favor the reverse direction.

Keep in mind that if you change the concentration or pressure, K does NOT change. If you change the temperature, K DOES change.


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