ICE Table

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Raashi Chaudhari 3B
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ICE Table

Postby Raashi Chaudhari 3B » Mon Jan 11, 2021 1:58 pm

Hi! I don't know if this is the correct place to put this question, but when making an ICE table and solving for the equilibrium concentrations, how do we know in the C row which side has the positive and negative values for x. I understand that the coefficients to x are the stoichiometric coefficients from the balanced reaction, but I have read on my Sapling to use Le Chatelier's Principle, and I am not really clear about what that entails.

Andrew Wang 1C
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Re: ICE Table

Postby Andrew Wang 1C » Mon Jan 11, 2021 2:02 pm

It depends on the value of Q relative to K. If Q is greater than K, then the reaction proceeds towards the reactants, so you would put "-x" on the products side and "+x" on the reactants side. If Q is less than K, then the reaction proceeds towards products and you would put "+x" for products and "-x" for reactants. (The coefficients of x would depend on the stoichiometric coefficients)

Hope this helps!
Last edited by Andrew Wang 1C on Mon Jan 11, 2021 2:03 pm, edited 1 time in total.

KatarinaReid_3H
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Re: ICE Table

Postby KatarinaReid_3H » Mon Jan 11, 2021 2:02 pm

Which ever side has an initial amount as zero will get the positive change and then the other side will have a negative change. If there is an initial amount for all of the species, usually the problem will give some indication of which will side will gain or lose. One example would be if the K value is given, you can find Q based on the initial species concentrations given and then figure out which way the rxn needs to go in order to reach equilibrium.

Arezo Ahmadi 3J
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Re: ICE Table

Postby Arezo Ahmadi 3J » Mon Jan 11, 2021 2:05 pm

For the concept of Le Chatelier's Principle, a reaction that is not at equilibrium is going to want to achieve an equilibrium state, which means that the reactants are going to be used up and the products are going to form. Since reactants are being used up, the change in their concentration is decreasing, so you would use a negative sign for their changes, and since products are forming, the change in their concentration is increasing, so you would use a positive sign for their changes.

Sophia Hu 1A
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Re: ICE Table

Postby Sophia Hu 1A » Mon Jan 11, 2021 2:05 pm

According to Le Chatelier's principle, the reaction will proceed to minimize change. For most ICE questions this is in regards to changes in concentration. If reactant is added, then we know the reaction will proceed to the right and produce products until equilibrium is reached. If products are added, then the reaction will proceed to the left and product reactants until equilibrium is reached.

This relates to the negative and positive signs for the change in concentration row because if we add a certain molar concentration of reactant, then the reaction would proceed to the right. The amount of reactants decrease (negative change) and the amount of products would increase (positive change).
If we added a certain molar concentration of product instead, the reaction would proceed to the left. The amount of reactants increase (positive change) as the amount of products decreases (negative change).

I hope this helps!

Juliet Cushing_2H
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Re: ICE Table

Postby Juliet Cushing_2H » Mon Jan 11, 2021 2:05 pm

Hi Raashi! The c value indicates a change occurring in the equilibrium. A lot of questions start off with reactants in a vessel and no products. In cases like these, the only change would be that reactants combine to form products: the amount of reactants decrease(-x) and the amount of products increase by the stoichiometric ratio(+x). If you had just products and no reactants, the change would be opposite: amount of products decrease(-x) so that reactants can be formed(+x) by the reverse reaction.

Some examples start at equilibrium with products and reactants on both sides, and additional moles are added to one side. In this case the reaction will attempt to come back to EQ such that Q=K. For this to happen, the side of the reaction that saw the initial increase will have an ice table change of (-x). Therefore the other side will see a change of (+x). I hope this helps!

anikamenon2H
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Re: ICE Table

Postby anikamenon2H » Mon Jan 11, 2021 2:14 pm

You put + when that species is being formed aka the product because it's molarity will increase. You subtract whatever species is being consumed, aka the reactants because it's overall molarity will increase. The coefficient in front of x is determined by the stoichiometric coefficients present in the chemical equation.

Hope this helps!

905290504
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Re: ICE Table

Postby 905290504 » Mon Jan 11, 2021 4:12 pm

use + for your products aka what is being formed and - for your reactants or what is being initially used. you should also multiply the x's by their stochiometric coefficients which can be found by balancing the chemical equation

KhanTran3K
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Re: ICE Table

Postby KhanTran3K » Mon Jan 11, 2021 4:22 pm

Hello!
Just to add on, the direction in which the reaction is moving -- whether that's towards the reactants or the products -- dictates which species are getting the nx or -nx in the ICE table. Usually, in some practice questions they will give you the initial concentration, so you can assume the species with the concentration of 0 will be the +nx since it will be increasing in concentration. When the concentration is given not at equilibrium, you can use the Q value to determine which way the reaction is going, and then determine which species would be increasing (the species in the direction the reaction is going) in concentration or decreasing (the species in the direction that the reaction is not going). Hope this helps! Feel free to correct me if I am wrong.

Namita Shyam 3G
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Re: ICE Table

Postby Namita Shyam 3G » Tue Jan 12, 2021 11:14 am

The way I was thinking about it was that if we increase concentration on one side (either reactants or products), then that side will be -x and the opposite side will be +x in the "Change" row. Sometimes, when all values in the "Initial" row are not equal to zero, the question will say which side increased, so based on that we will know to make the opposite side +x.


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