ice tables?

[Dalia Torres 3I]

Hi! I am still a bit confused and was wondering if anyone could help??

When do you know when to make it positive or negative when setting up an ICE table??

[Maia Hull 1H]

A value will be negative when it is on the reactant side of the equation, because that concentration is going to go down as the reaction proceeds and it is turned into product. And that it why the product values will be positive, because their concentration will increase as the reaction goes on. Hope this helps!

[jkenn123]

For me what helps is everything to the right of the 0 is going to be -x, because it's being used. So if you have 1.5 0 0 then it would be -x, +x, +x. I hope that kind of makes sense.

[505823976]

So a ice table will have x being subtracted from the initial concentration of the reactants and then x will be added to the products.
https://youtu.be/1GiZzCzmO5Q
please follow this video its really quick and clear on why and explain the concept very well!

[Maribel 1E]

If you are referring to the change in concentration in ice tables (when to make the change, being x, positive or negative), it depends on whether it is a change in the reactants or products. If you are doing a change of the reactants, then you would subtract x (-x) since the reactants are being consumed in the reaction. If you are doing a change of the products, you would add x (+x) since the products are being made and produced in the reaction. Hope this helps!

[Lauren Williams 1B]

It will tell usually tell you what the initial concentration of a molecule is in the problem. Determine whether this molecule is in the reactants or products side. If it is on the reactants side, the reaction would move towards products to balance it. This means that we will be decreasing the initial concentration by x per mole. If there were two moles it would be 2x, etc. Because we are subtracting from the reactants side (in this example) we would be adding to the products side. So we would add an x for each mole of each product.

[Rhea Jain 2I]

What exactly are you referring to for your question about positive and negative? Regardless, here's some steps to help outline and an example (btw, I call it a RICE table because I like to write the reaction at the top because then it's easier to fill each line under each component of the reaction):

R (reaction)
I (initial conc.)
C (change in conc.)
E (equilibrium)

Step 1: Write the reaction at the top in the "R" line
Step 2: Fill in the given amounts in the problem in the "I" line
Step 3: Fill in the amount of change for each compound with respect to "x" in the "C" line, which you should be able to tell by looking at the reaction
Step 4: Solve for the equilibrium amounts by combining what you wrote in the "I" and "C" lines and filling it in the "E" line

EXAMPLE:

R HClO2(aq) + H2O(l) →  H3O+(aq) + ClO2-(aq)
I 0.1 - 0 0
C -x - +x +x
E 0.1-x - x x

NOTES:
- phases that aren't aqueous are negligible (not included in the ICE table)
- reactants are being used up which is why their change of x is negative
- products are being made which is why their change of x is positive

I hope this helps!

[Erika McKee 2G]

Hi! If you are referring to making the x value positive or negative in the ICE table, usually the x will be subtracted from the larger concentration. So, if there are more reactants the x would be subtracted from that and added to the products when the equation is going towards equilibrium, and vice versa if the product concentration is greater.

[Emily_Hanna_2E]

Hi Dalia!
When you set up the equation and you have a starting concentration of a molecule on one side of the equation, typically you would subtract x from this and add x to the other side where the starting concentration is 0. Part of it is because you cannot subtract x (times the coefficient of the molecule in the equation for any x you add/subtract) from a molecule with a starting concentration of 0. Also, when there is more concentration on one side, it will want to go to the other side to balance out. Keep in mind that with water, you would not make it part of the ice chart! Hope this was helpful!

[aestraw2213]

The reactants produce negative values because they are getting subtracted as they react and turn into products. Thus, the products have positive values because initially they are nothing, then as a reaction occurs they increase as reactants become products.

[Reynaldo Fernandez 3L]

First, you determine which direction the reaction will go in before you should choose. You do this by comparing the reactant and product starting concentrations to their equilibrium concentrations. If the products’ equilibrium concentrations are higher than its initial concentration, the reaction is moving from reactants to products, and the reactants values in the ICE table should be negative while the products positive. And if the reactants’ equilibrium concentration is higher than its initial concentration, the reaction is moving from products to reactants, and the change in the ICE table for the reactants should be positive while the products negative.

[505968894]

ICE tables are useful when the amount of one reactant or product must be determined from given information about another product or reactant.