Question

In the detection of III group basic radicals $N{H_4}OH$ is added after $N{H_4}Cl$ to
A. Increase in the ionization of $N{H_4}OH$
B. Increase in the ionization of salt solution
C. Decrease in the ionization of salt solution
D. Decrease in the ionization of $N{H_4}OH$

Answer 1

We can say the decrease in solubility of an ionic compound by the addition to the solution of soluble compound contains common ions. That common ion lessens the solubility of the compound. We can call this effect the common ion effect.

Complete step by step answer: We have to know a substance that conducts electricity in water is called an electrolyte and a substance that does not conduct electricity in water is called a nonelectrolyte.
An electrolyte that completely dissociates to form ions, when it dissolves in water is called a strong electrolyte.
An electrolyte, in which a small fraction of molecules forms ions when dissolved in water to give largely uncharged molecules, is called a weak electrolyte.
Let us know $N{H_4}Cl$ is a strong electrolyte and hence it undergoes dissociation completely. Whereas, $N{H_4}OH$ is weak electrolyte so it dissociates partially. This is because of presence of common ion $N{H_4}^ +$ in $N{H_4}Cl$ it suppresses the ionization of weak base $N{H_4}OH$ in order to reduce the concentration of $OH$. Therefore, those higher group cations would not precipitate. So, we add $N{H_4}Cl$ to reduce the ionization of $N{H_4}OH$ to avoid precipitation of higher group elements.
Because of this, group Ill hydroxides are precipitated having lower solubility products.
Therefore, option (D) is correct.

Note: The salting-out process used in the preparation of soaps benefits from the common-ion effect. We know that soaps are sodium salts of fatty acids. Addition of sodium chloride decreases the solubility of the soap salts. The precipitation of soap happens due to a combination of common-ion effect and increased ionic strength. Sea, brackish and other waters which have considerable amounts of sodium ions interfere with the usual behavior of soap due to common-ion effects. During the presence of excess sodium, the solubility of salts of soap gets reduced, thereby making the soap less effective.