Question

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

Answer 1

Answers are in the explanation.

Step-by-step explanation:

Given concentrations are:

• SO₂ = 0.20M O₂ = 0.60M SO₃ = 0.60M

• SO₂ = 0.14M O₂ = 0.10M SO₃ = 0.40M

• And SO₂ = 0.90M O₂ = 0.50M SO₃ = 0.10M

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:

• Q = [0.60M]² / [0.60M] [0.20M]² = 15; Q = Kc → No net reaction

• Q = [0.40M]² / [0.10M] [0.14M]² = 82; Q > Kc, → Reaction will shift to the left

• Q = [0.10M]² / [0.50M] [0.90M]² = 0.015; Q < Kc → Reaction will shift to the right