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# What is a solubility product? Establish the relation between solubility and solubility product for CdS type compounds. In third group analysis, $N{H_4}Cl$ is added before $N{H_4}OH$, Why?

Last updated date: 29th Feb 2024
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Hint: A solid, liquid, or gaseous chemical compound ability to dissolve in a solvent (usually a liquid) and form a solution is known as solubility. A substance's solubility is largely determined by the solvent used, as well as temperature and pressure.

Solubility Product:
It is defined as the product of the ion concentrations in a saturated electrolyte solution at a given temperature. The symbol ${K_{sp}}$ is used to represent it.
As salt is dissolved in a solvent, the interactions between ions and the solvent must counteract the strong forces of attraction of the solute (lattice enthalpy of the ions).
Ions have a negative solvation enthalpy, which ensures that energy is released during the process.
The nature of the solvent determines the amount of energy released during solvation that is solvation enthalpy.
The solvation enthalpy of non-polar solvents is low, indicating that this energy is insufficient to resolve the lattice enthalpy.
As a result, non-polar solvents cannot dissolve the salts. As a result, a salt's solvation enthalpy must be greater than its lattice enthalpy in order for it to dissolve in a solvent.
For CdS form compounds, there is a relationship between solubility and solubility products.
Let x be the CdS solubility.
${\mathbf{CdS}} \rightleftharpoons {\mathbf{C}}{{\mathbf{d}}^{2 + }} + {{\mathbf{S}}^{\mathbf{2}}}$
${{\mathbf{K}}_{{\text{sp}}}} = \left[ {{\mathbf{C}}{{\mathbf{d}}^{2 + }}} \right]\left[ {{{\mathbf{S}}^{2 - }}} \right]$
${{\mathbf{K}}_{{\text{sp}}}} = = ({\text{x}}) \times ({\text{x}})$
${{\mathbf{K}}_{{\text{sp}}}} = {{\mathbf{x}}^2}$
B.
Since the $N{H_4}^ +$ ions supplied by $N{H_4}Cl$lower the ionisation of $N{H_4}OH$ and hence the concentration of $O{H^ - }$ ion in the third group study, $N{H_4}Cl$ is added before $N{H_4}OH$. Hydroxides of the III group form at low $O{H^ - }$ ion concentrations. The precipitation of group hydroxides occurs when $N{H_4}OH$ is added in the presence of $N{H_4}Cl$.

Note:
The description of the cation and anion of an inorganic salt is known as salt analysis (also known as systematic qualitative analysis or qualitative inorganic analysis). This may be accomplished by defining the cation and anion of the salt separately.