At a certain temperature, the equilibrium constant Kc is 117 for the reaction 2SO3(g) ⇀↽ 2SO2(g) + O2(g)

Question

At a certain temperature, the equilibrium constant Kc is 117 for the reaction 2SO3(g) ⇀↽ 2SO2(g) + O2(g) When the reaction reaches equilibrium at this temperature we measure 0.750 moles of SO3 and 0.645 moles of O2 in a 1.00 liter container. What is the concentration of SO2?

1. 102 M

2. 12.6 M

3. 11.7 M

4. 158 M

5. 10.1 M

6. 136 M

Answer 1

Hi Nick!

For this question, we have to look at the equilibrium expression for the reaction. Since we have a balanced reaction, we can use the coefficients to write it out. Remember, when we write out the equilibrium expression, whatever coefficients we have for the products or reactants become their respective exponents.

K = [Products] / [Reactants]

K_c = [SO₂]² * [O₂] / [SO₃]²

Now, the brackets indicate molar concentration, so we have to make sure that we have everything in mol/L. Thankfully, in this problem, everything was given in 1 liter, so no calculation of morality is required! So if we plug in our numbers, we'll end up with...

117 = [SO₂]² * [.645] / [.750]²

And when we work out the math, and solve for SO₂ on it's own, it works out to 10.10. Hope that helps!

-Niral