Question

For the reaction 2 SO 2 ( g ) + O 2 ( g ) − ⇀ ↽ − 2 SO 3 ( g ) the equilibrium constant is K c = 15 M − 1 at 850 K . Three sets of concentrations are given for the three gases in the reaction. For each set, predict the direction in which the net reaction will proceed toward equilibrium. Left No net reaction Right (SO2)=0.16M (SO2)=0.20M (SO2)=0.50M (O2)=0.20M (O2)=0.60M (O2)=0.60M (SO3)=0.50M (SO3)=0.60M (SO3)=0.15M

Answer 1

2SO₂(g) + O₂(g) ↔ 2SO₃(g) Kc = 15M⁻¹

The sets are:

(A) (SO₂)=0.16M; (O₂)=0.20M; (SO₃)=0.50M

(B) (SO₂)=0.20M; (O₂)=0.60M; (SO₃)=0.60M

(C) (SO₂)=0.50M; (O₂)=0.60M; (SO₃)=0.15M

The reaction quotient is

Q =
`([SO_(3)]^2)/([SO_(2)]^(2)*[O_(2)] )`

• If Q < Kc, then the reaction will proceed towards the right (products)

• If Q > Kc, then the reaction will proceed towards the left (reactants)

• If Q = Kc, then we're at equilibrium.

Now we calculate Q for each of the sets:

(A) Q = 0.50² / (0.16²*0.20) = 48.8

Q > Kc. So the reaction will proceed towards the left.

(B) Q = 0.60² / (0.20²*0.60) = 15

Q = Kc. So the reaction is at equilibrium.

(C) Q = 0.15² / (0.50²*0.60) = 0.15

Q < Kc. So the reaction will proceed towards the right.