Calculating Kc

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Marisa Gaitan 2D
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Calculating Kc

Postby Marisa Gaitan 2D » Thu Jan 07, 2021 9:37 am

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.
At equilibrium, 0.120 mol O2 is present.

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

Posts: 107
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Re: Calculating Kc

Postby Lindsey_Su_3A » Thu Jan 07, 2021 9:46 am

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
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Joined: Wed Sep 30, 2020 9:53 pm

Re: Calculating Kc

Postby marlene 1K » Thu Jan 07, 2021 10:52 am

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
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Joined: Wed Nov 18, 2020 12:25 am

Re: Calculating Kc

Postby Kiran Marla » Thu Jan 07, 2021 11:45 am

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
Posts: 73
Joined: Wed Sep 30, 2020 9:35 pm

Re: Calculating Kc

Postby Katie Le 3K » Thu Jan 07, 2021 6:08 pm

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

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