On ICE table (1 Viewer)

[NexusRich]

What are ICE table used for and when do we use them ?

 

[Sp3ctre]

They're used for finding equilibrium constants (K) when you don't have sufficient information to calculate K directly using the formula.
You'll usually need to use it when the question gives you a chemical equation and some small bits of information such as initial moles or concentration, but without giving you the equilibrium concentrations of everything in the equation (which is what you need when using the formula).

This is a neat example I yoinked from another forum which could help you understand it a bit better:

0.10 mol of N2O4 is allowed to come to equib in a 2.0 L flask according to the following reaction:
N2O4(g) <---> 2NO2(g)
At equib, there are 0.060 mol of NO2. Determine K

To determine K, we need the equilibrium concentrations of both the reactants and products (I'm assuming you're familiar with the K formula already)
However, all we are given from this question is the initial moles of N2O4 and the final (equilibrium) moles of NO2. This is when we need to set up the ICE table.

	N2O4	NO2
I - initial n	0.10
C - change in n
E - equilibrium n		0.060

The most obvious place to start is the initial moles of 2NO2. There shouldn't be products initially, so initial n(NO2) = 0.

Now we can work out the change in moles of 2NO2 since we have both initial n(NO2) and equilibrium n(NO2).
Change in n(2NO2) = 0.060 - 0 = +0.060 mol. Pretty straightforward!

Now pay attention to the mole ratio of the equation. It's a 1:2 ratio, which means for every mole of N2O4, 2 moles of NO2 are produced.
Therefore, change in n(N2O4) = 0.060 / 2 = -0.030 mol. Keep in mind that this value is negative since N2O4 is the reactant.

Finally, we can now easily find the moles of N2O4 at equilibrium.
n(N2O4) at equilibrium = 0.10 - 0.030 = 0.07 mol.

	N2O4	NO2
I - initial in n	0.10	0
C - change in n	-0.030	+0.060
E - equilibrium n	0.07	0.060

That's all you need to use the ICE table for. But to finish the question, you need to use the equilibrium moles that we found using the ICE table to find the equilibrium concentrations using n = c / v, then use those concentrations to find K. Hope that helps!

 

[NexusRich]

They're used for finding equilibrium constants (K) when you don't have sufficient information to calculate K directly using the formula.
You'll usually need to use it when the question gives you a chemical equation and some small bits of information such as initial moles or concentration, but without giving you the equilibrium concentrations of everything in the equation (which is what you need when using the formula).

This is a neat example I yoinked from another forum which could help you understand it a bit better:

0.10 mol of N2O4 is allowed to come to equib in a 2.0 L flask according to the following reaction:
N2O4(g) <---> 2NO2(g)
At equib, there are 0.060 mol of NO2. Determine K

To determine K, we need the equilibrium concentrations of both the reactants and products (I'm assuming you're familiar with the K formula already)
However, all we are given from this question is the initial moles of N2O4 and the final (equilibrium) moles of NO2. This is when we need to set up the ICE table.

	N2O4	2NO2
I - initial n	0.10
C - change in n
E - equilibrium n		0.060

The most obvious place to start is the initial moles of 2NO2. There shouldn't be products initially, so initial n(2NO2) = 0.


Now we can work out the change in moles of 2NO2 since we have both initial n(2NO2) and equilibrium n(2NO2).
Change in n(2NO2) = 0.060 - 0 = +0.060 mol. Pretty straightforward!

Now pay attention to the mole ratio of the equation. It's a 1:2 ratio, which means for every mole of N2O4, 2 moles of NO2 are produced.
Therefore, change in n(N2O4) = 0.060 / 2 = -0.030 mol. Keep in mind that this value is negative since N2O4 is the reactant.

Finally, we can now easily find the moles of N2O4 at equilibrium.
n(N2O4) at equilibrium = 0.10 - 0.030 = 0.07 mol.

	N2O4	2NO2
I - initial in n	0.10	0
C - change in n	-0.030	+0.060
E - equilibrium n	0.07	0.060

That's all you need to use the ICE table for. But to finish the question, you need to use the equilibrium moles that we found using the ICE table to find the equilibrium concentrations using n = c / v, then use those concentrations to find K. Hope that helps!

Thank you so much!!!!! I understand it now

 

[Sp3ctre]

Thank you so much!!!!! I understand it now

No worries, glad to hear!