Question

According to the reaction $PbC{{l}_{2}}\to P{{b}^{+2}}+2C{{l}^{-}}$ the solubility coefficient of lead chloride​ is:
A. \[[P{{b}^{+2}}]{{[C{{l}^{-}}]}^{2}}\]
B. \[[P{{b}^{+2}}][C{{l}^{-}}]\]
C. \[[P{{b}^{+2}}]2[C{{l}^{-}}]\]
D. None of these

Answer 1

Hint: Solubility product depends on the concentration of ions formed in a reaction at equilibrium. Lead chloride dissociates into lead cation and chloride ion. Thus the solubility coefficient depends on the concentration of the cation and anion.

Complete Step by Step Answer:
Solubility product or solubility coefficient of a species is defined as the product of the concentration of the cation and anion formed from a species at equilibrium. At this stage the coefficients before the ions exist as a power to the concentration of the corresponding cation and anion.

Lead chloride dissociate at equilibrium as follows:
$PbC{{l}_{2}}\to P{{b}^{+2}}+2C{{l}^{-}}$
Thus two will exist as a power on the concentration of the anion that is chloride ion.
Thus solubility product is given as follows:
$K_{sp}=(S)\times S$; where $Ksp$ is defined as the solubility product and $S$ is defined as the concentration for the cation and anion.
It is given as follows:
$K_{sp}=[P{{b}^{+2}}]{{[C{{l}^{-}}]}^{2}}$
Thus the correct option is A.

Note: Concentration is a ratio of mass to volume of a particular substance. It is expressed in the unit of mole per litre. Concentration is an intensive property. The rate of reactions, solubility product etc are generally expressed in terms of concentration.