At 850 K, the equilibrium constant for the reaction 2SO2(g)+O2(g)↽−−⇀2SO3(g)
is Kc=15. If the given concentrations of the three gases are mixed, predict in which direction the net reaction will proceed toward equilibrium.
Left No net reaction Right

Answers are in the explanation.

Explanation:

Given concentrations are:

In the reaction:

2SO₂(g) + O₂(g) ⇄ 2SO₃(g)

Kc is defined as:

Kc = 15 = [SO₃]² / [O₂] [SO₂]²

Where concentrations of each species are equilbrium concentrations.

Also, you can define Q (Reaction quotient) as:

Q = [SO₃]² / [O₂] [SO₂]²

Where concentrations of each species are ACTUAL concentrations.

If Q > Kc, the reaction will shift to the left until Q = Kc;

If Q < Kc, the reaction will shift to the right until Q = Kc

If Q = Kc, there is no net reaction because reaction would be en equilibrium.

Replacing with given concentrations:

the answer is option a.