Calculating Kc

[Marisa Gaitan 2D]

In Sapling question 2 for week 1, it gives us:

At a certain temperature, 0.680 mol SO₃ is placed in a 2.50 L container.
2SO₃(g)↽−−⇀2SO₂(g)+O₂(g)
At equilibrium, 0.120 mol O₂ is present.

It asks to calculate K_c. How would you approach this problem?

[Lindsey_Su_3A]

In this question, they give you the initial concentration of the reactant and the equilibrium concentration of one of the products. You can use the Equilibrium table that follows Initial, Change, and Equilibrium concentrations.

[marlene 1K]

You're given the initial and equilibrium. So first I drew out the ICE table, then converted the mols to mols.L-1 by dividing the mols by the liters they give you (you can also do this at the end), then filled in the ICE box. To find the change for the 2 unknown, i multiplied the known equilibrium by the stoichiometric coefficients, then added them to the change by subtracting and got the equilibrium for the 2 unknown and then plugged it into the Kc=[P]/[R] equation. Hope that helps!!

[Kiran Marla]

The key for this question is to draw an ICE table. You are given initial conc of SO3, and you are given the eq conc of O2. You already know the change because of the coefficients. Using this, you can add/subtract changes from initial conc, and find all the eq conc. This will allow you to find Kc

[Katie Le 3K]

You use the ICE chart. If you click feedback, Sapling should provide one for you.