LeChatelier's Lunacy
Example Problem

Consider the following equilibrium

2SO₂(g) + O₂(g) ⇔ 2SO₃(g) DH=-197.78 kJ

1. Write the expression for the equilibrium constant, K_c, for this equilibrium
2. A mixture of SO₂(g), O₂(g) and SO₃(g) at 852K is allowed to reach equilibrium. The concentrations at equilibrium are found to be:
   
   [SO₂] = 3.61 × 10^-3 mol/L, [O₂] = 6.11 × 10^-4 mol/L, [SO₃] = 1.01 × 10^-3 mol/L.
   
   Calculate the equilibrium constant, K_c for the system at 852K, including the correct units.
3. What would be the effect on the concentration of O₂(g) and the value of Kc, if the following changes were made to the system described above. For your answer use “I” for increase, “D” for decrease and “R” for remains the same.

   		[O2]	Kc
   i.	Some SO3(g) is removed from the system	________	_________
   ii.	The volume is lowered at constant temperature, raising the pressure.	________	_________
   iii.	The temperature of the system is raised	________	_________
   iv.	A catalyst is added	________	_________
   v.	Helium is added to the system	________	_________
   vi.	Some SO2(g) is added to the system	________	_________
   vii.	A small piece of Mg is ignited in the flask, after which the temperature is returned to 852K	________	_________

4. At a different temperature, the equilibrium constant, K_c, for this system would be 963. In an equilibrium mixture at the new temperature [O₂] = 0.463 mol/L, and [SO₃] = 0.821 mol/L. Calculate the concentration of SO₂ in the system.
5. At the temperature mentioned in d), a previously empty 5.00L flask is prepared by adding 1.20 mol of SO₂ and 1.50 mol of O₂. Determine the concentrations of SO₂, O₂ and SO₃ once equilibrium is established.
6. At yet a third temperature, the K_c for this system would be 4.20 × 10^-2. Initially a mixture at equilibrium in a 1.00 L flask contains the following concentrations
   
   [SO₂] = 1.40 mol/L, [O₂] = 11.00mol/L, and [SO₃] = 0.906 mol/L.
   
   If an additional 2.00 moles of O₂ are added to the flask, what will be the concentrations of the SO₂, O₂ and SO₃ once equilibrium is reestablished?