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

The correct option is D decrease in the ionization of $N{H}_{4}OH$

Here is the judgement. $N{H}_{4}Cl$ is strong electrolyte and hence it decomposes completely. While $N{H}_{4}OH$ is weak electrolyte so it decomposes partially. Thus due to presence of common ion $N{H}_4^{+}$ in $N{H}_{4}Cl$, it supresses the ionisation of weak base $N{H}_{4}OH$ in order to decrease concentration of $O{H}^{-}$ so that higher group cations will not precipitate. So, we add $N{H}_{4}Cl$ to decrease the ionization of $N{H}_{4}OH$ to prevent from precipitation of higher group elements.