Question

Is the solution containing 0.20 M Pb2 and 0.10 M Cl (Ksp 1.6x105) a) saturated, b) unsaturated, c) at equilibrium, d) none of the above

Answer 1

Answer : The correct option is, (b) unsaturated

Explanation :

Ionic product : It is defined as the product of the concentrations of the ions present in solution raised to the same power by its stoichiometric coefficient in a solution of a salt. This takes place at any concentration. The ionic product is represented as, Q.

Solubility product constant : It is defined as the product of the concentration of the ions present in a solution raised to the power by its stoichiometric coefficient in a solution of a salt. This takes place at equilibrium only. The solubility product constant is represented as, $K__{sp}$.

Now we have to calculate the ionic product of given solution.

The balanced chemical reaction is,

$PbCl_2(aq)\rightarrow Pb^{2+}(aq)+2Cl^-(aq)$

The expression of ionic product will be,

$Q=[Pb^{2+}][Cl^-]^2$

$Q=(0.20)\times (0.10)^2$

$Q=0.002$

The ionic product of solution is, 0.002

There are three cases for the solubility :

When $Q$ this means that the solution is unsaturated solution and more solid will be dissolve.

When $Q=k_{sp}$ this means that the solution is saturated solution.

When $Q>k_{sp}$ this means that the solution is supersaturated solution and solid will be precipitate.

From this we conclude that the value of $k_{sp}=1.6\times 10^5$ is greater than the ionic product that means the solution is unsaturated solution and more solid will be dissolve.

Hence, the correct option is, (b) unsaturated