JEE Main 2024 Chemistry question

Chemistry Principles Related to Practical Chemistry JEE Main 2024

In the precipitation of the iron group (III) in qualitative analysis, ammonium chloride is added before adding ammonium hydroxide to:

(A)prevent interference by phosphate ions
(B)decrease concentration of OH ionsCorrect
(C)increase concentration of Cl ions
(D)increase concentration of NH ions

Answer: (B)

Solution

Common-ion effect of NH₄⁺ suppresses ionisation of NH₄OH, so only the very insoluble group-III hydroxides ( ~ 10⁻³⁸) precipitate.

Question ID VK-011432