Moderators: Chem_Mod, Chem_Admin

Jenny Chau 1I
Posts: 119
Joined: Wed Sep 30, 2020 9:33 pm


Postby Jenny Chau 1I » Thu Jan 14, 2021 12:40 am

I hope this isn't a dumb question but how do we know when to use ICE as opposed to just plugging in values into: Kc = [products]/[reactants]? I've been doing problems the latter way when the problem is solved through ICE in the answer key.

Darlene Lien 3E
Posts: 113
Joined: Wed Sep 30, 2020 9:37 pm


Postby Darlene Lien 3E » Thu Jan 14, 2021 12:47 am

Hi, generally you would use ICE charts to help when you have an initial concentration and an equilibrium concentration. When you solve for the change in concentration, you are able to get the equilibrium concentrations and use Kc accordingly. Typically, when the question gives or states that the concentrations are all at equilibrium or such then you could simply plug in these values and use Kc directly. However, I think it's important to keep in mind that you don't have to use an ICE chart either, but it could help with organization and for visuals. Hope this helps!

Posts: 86
Joined: Wed Sep 30, 2020 9:51 pm
Been upvoted: 1 time


Postby HannahRobinson3L » Thu Jan 14, 2021 12:51 am

ICE is never necessary. It is a way of organizing the information you're given and finding your answer in a clear way. Now, you do have to use the placeholder of x to find out exactly how much the concentration or partial pressure changed. I'm not a hundred percent sure exactly what you mean by just plugging in to the expression: if you are just plugging in the values given in the problem, or if you are doing the ICE chart in your head and putting the proper expressions for each concentration. Assuming you are doing the prior, you are probably using the initial values, which aren't correct because the question is asking for the value at equilibrium. The easiest way to tell if you need to use ICE is if they give you the values of the concentration at equilibrium or initially. If they give you initial concentrations, you have to use ICE and solve for x.

Pranav Daggubati 3C
Posts: 109
Joined: Wed Sep 30, 2020 9:35 pm


Postby Pranav Daggubati 3C » Thu Jan 14, 2021 8:23 am

You can use ICE charts when finding how much a concentration changed when going to equilibrium, which allows you to find al of the equilibrium concentrations, and then calculate Kc using that.

Posts: 92
Joined: Wed Sep 30, 2020 9:33 pm


Postby Juwan_Madaki_3K » Thu Jan 14, 2021 9:31 am

I think it's especially important to pay attention to the words "equilibrium" and "initial". If only equilibrium concentrations are present, then I think it's safe to assume that the ICE tables aren't necessary. However, if initial concentrations are present, then using an ICE table is necessary.

Anna Yang 1A
Posts: 98
Joined: Wed Sep 30, 2020 9:43 pm


Postby Anna Yang 1A » Thu Jan 14, 2021 9:41 am

It's just a means of organization to help you better see your known and unknown values and how values find relation to each other (such as x-something is one substance's concentration at equilibrium while x or coefficient*x is another substance's concentration).

Jaclyn Dang 3B
Posts: 105
Joined: Wed Sep 30, 2020 10:02 pm


Postby Jaclyn Dang 3B » Thu Jan 14, 2021 10:05 am

I usually think of using ice when the problem gives you an initial concentration and ask you to determine the final concentration at equilibrium. Hope this helps.

Chloe Shamtob 2H
Posts: 108
Joined: Wed Sep 30, 2020 9:55 pm


Postby Chloe Shamtob 2H » Thu Jan 14, 2021 10:17 am

To figure out whether to use a ice table or the equilibrium constant equation you must pay attention to what is given in the problem. If you are given the initial concentrations of the reactants and an equilibrium concentration, you should use the ICE table to find the concentrations of the products and reactants at equilibrium. If you are given all the concentrations at equilibrium already and are asked to find Kc, then you should plug the values into the equilibrium constant equation to find Kc.

Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 2 guests