ICE problems

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Jasmin Argueta 1K
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ICE problems

Postby Jasmin Argueta 1K » Thu Jan 24, 2019 10:10 pm

In regards to doing ICE problems, I'm a bit confused for the "change" section. I know we are suppose to include coefficients on the x value if there is a molarity given, although how do you know if the x value is positive or negative?

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Re: ICE problems

Postby Chem_Mod » Thu Jan 24, 2019 10:20 pm

If the reaction is going forward, the reactants decrease (negative), and the products increase (positive).

Madeline Motamedi 4I
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Re: ICE problems

Postby Madeline Motamedi 4I » Fri Jan 25, 2019 6:45 pm

You are always adding a the change to the concentrations, whether thats positive or negative, it doesn't matter, you will find out after solving. But in terms of weather you are subtracting the x or adding the x, if you are starting with all reactants and no products, you are going to have to subtract from some of the reactants in order to make some products. On the other hand, if you have both an initial concentration of products and reactants, you have find Q and compare it to your K and see which direction the reaction will proceed. That direction will tell you if you subtract a change from your products and add it to reactants and vice versa.

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Re: ICE problems

Postby LilyL1C » Fri Jan 25, 2019 8:09 pm

It depends on which way the reaction is going.
If it is a forward reaction, then reactants are getting turned into products, so you would subtract the change from the reactants and add the change to the products.
If it a reverse reaction, then the products are getting turned into reactants, so you would subtract the change from the products and add the change to the reactants.

Amar Singh
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Re: ICE problems

Postby Amar Singh » Sun Jan 27, 2019 2:58 pm

Usually you will know in the problem which way the reaction is proceeding. Most of the times it will be the forward reaction that is favored, but occasionally it will be the reverse reaction. Sometimes the concentrations of the products and reactants are given, so you might have to calculate Q and use that to see where the reaction is heading. Once you know that, you can determine which change would be negative and positive. For example, if the forward reaction is favored, then the reactants would be subtracted from (because they are being turned into products), and the products would be added to (because they are being formed).

Emilia z
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Re: ICE problems

Postby Emilia z » Sun Jan 27, 2019 3:06 pm

The change refers to what change is happening to that species, and we use x because we don’t know the exact amount that changes (either taken away or added/created)

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