Question

At 850 K, the equilibrium constant for the reaction 2SO₂(g)+O₂(g)↽−−⇀2SO₃(g) is ?c=15. If the given concentrations of the three gases are mixed, predict in which direction the net reaction will proceed toward equilibrium. 

Answer 1

Answer -

Given,

Temperature = 850 K

Kc = 15

2SO₂ (g) + O₂ (g)   $\rightleftharpoons$ 2 SO₃ (g)

Set 1 - [SO₂] = 0.60 M, [O₂] = 0.50 M, [SO₃] = 0.10 M

Set 2 - [SO₂] = 0.20 M, [O₂] = 0.60 M, [SO₃] = 0.60 M

Set 3 - [SO₂] = 0.13 M, [O₂] = 0.20 M, [SO₃] = 0.50 M

Direction of Shift = ?

We have to calculate Q_c for this. Q_c is calculated similarly as Kc. Only difference is that K_c is calculated at equillibrium and Q_c can be calculated at any Temperature

Also,

If K_c = Q_c--------------No net reaction

If K_c > Q_c--------------Towards Right

If K_c < Q_c--------------Towards Left

So, in SET 1

Q_c = [SO₃]²/[SO₂]²[O₂]

put the values,

Q_c = [0.10]²/[0.60]²[0.50]

Q_c = 0.055

0.055 is less than 15

So, Q_c is less than K_c

_{The reaction will shift towards Right.}

So, in SET 2

Q_c = [SO₃]²/[SO₂]²[O₂]

put the values,

Q_c = [0.60]²/[0.20]²[0.60]

Q_c = 15

So, Q_c is equal to K_c

_{There will be no net reaction.}

So, in SET 3

Q_c = [SO₃]²/[SO₂]²[O₂]

put the values,

Q_c = [0.50]²/[0.13]²[0.20]

Q_c = 73.96

So, Q_c is greater to K_c

_{The reaction will shift towards Left.}