1.1. Some industrial processes involve reversible reactions. If done under the correct conditions, then these reactions will reach a dynamic equilibrium, producing equilibrium mixtures of reactants and products. The conditions of the reaction can be altered and controlled to maximise the product yield. 

Le Chatelier’s principle is a rule which is used to determine how to move the equilibrium position to the left or right, by altering specific conditions of the reaction.  

State Le Chatelier’s principle. 

1.2. An example of an equilibrium reaction can be seen between oxygen and nitrogen.

When heated to a high enough temperature, nitrogen will react with oxygen to form nitrogen monoxide, as shown below:

N₂ (g) + O₂ (g) ⇋ 2NO (g)

When the temperature of the system is increased, the yield of NO increases. 

State whether the forward reaction in this system is exothermic or endothermic. Explain your answer. 

1.3. State and explain the effect, if any, on the yield of NO produced if the pressure was increased, but the temperature was kept the same.

1.4. A chemist set up a different reaction, shown below:

W (aq) + 2X (aq) ⇋ 3Y (aq) + Z (aq)

They started with a flask containing 1.75 x 10^-2 mol of an aqueous solution W. They then added 0.050 mol of solution X to the flask, ensured a closed system, and allowed the reaction to reach equilibrium. 

Once equilibrium was reached, the reaction mixture contained 0.012 mol of Z. 

The overall volume of the reaction mixture was 105 cm³. 

i) Give the K_c expression for this reaction.

[1]

ii) Calculate a value for K_c .

[5]