Question

PbCl2 (s) ==== Pb2+ (aq) + 2 Cl- (aq)

Record your observations for the following changes and explain each in term of Le Chatelier’s principle. Write net ionic equations for the reactions which occur.

1. Heating the PbCl2 mixture.

2. Addition 1.0 M Na2CO3 to the clear liquid.

3. Reaction with 1.0 M HNO3.

4. Reaction with Na2S.

Answer 1

H of the reaction is +23.41KJ, thus it is an endothermic reaction.

1. Heating the reaction would be favourable, since endothermic reaction require heat. Thus, equilibrium will shift towards the right.
2. Addition of Na₂CO₃ will cause the formation of PbCO₃, which is a precipitate. Thus, it will take Pb²⁺ ions out of the solution and drive the reaction in the forward direction.
3. Addition of HNO₃ will have no effect on the equilibrium because the salt formed, i.e Pb(NO₃)₂ is soluble in water, thus Pb²⁺ ions will still be in the solution.
4. Reaction is driven in the forward direction, reason same as #2.