solving concentration from chem. equilibrium (sapling #3)

[dana hu 1B]

Hello. I ran into a problem where after solving all the values to plug into solving the Kc and then using the quadratic formula, what happens when I end up with two different positive concentrations?
Thank you!

[Lillian Ma 1I]

In this question, I believe you would take the smaller number because the larger one is bigger than the initial concentration, which is not possible. However, in general I'm not sure which one you'd pick if both were possible numbers.

[Stuti Pradhan 2J]

For this problem, you can take the square root of both sides after setting up the ratio, so you do not need to solve a quadratic equation. Typically, if you have two positive concentrations, the one that is larger than the initial concentrations is incorrect.

Hope this helps!