Which of the following happens when NH_4 OH is added gradually to the solution containing 1 M A^ 2+ and 1 MB^ 3+ ions? Given : K_ sp [A(OH)_2]=9 × 10^ -10 and K_ sp [B(OH)_3]=27 × 10^ -18 at 298 K .

Correct answer: C. B(OH)_3 will precipitate before A(OH)_2 Condition for precipitation Q_ ip >K_ sp For [A(OH)_2] aligned & [A^ 2+ ][OH]^2>9 × 10^ -10 & [ A^ +2 ]=1 M & [OH^ - ]>3 × 10^ -5 M aligned For [B(OH)_3] aligned & [B^ 3+ ][OH^ - ]^3>27 × 10^ -18 & [ B^ 3+ ]=1 M & [OH^ - ]>3 × 10^ -6 M aligned So, B(OH)_3 will precipitate before A(OH)_2

JEE Main 202523 JanuaryMorning Shift

Exam: JEE Main
Year: 2025
Date: 23 January
Shift: Morning Shift
Subject: Chemistry
Chapter: Ionic Equilibrium

JEE Main 2025 · 23 January · Morning Shift · Chemistry · Ionic Equilibrium

Which of the following happens when NH_4 OH is added gradually to...

Which of the following happens when

\mathrm{NH}_4 \mathrm{OH}

is added gradually to the solution containing 1 M

\mathrm{A}^{2+}

and

1 \mathrm{MB}^{3+}

ions? Given :

\mathrm{K}_{\mathrm{sp}}\left[\mathrm{A}(\mathrm{OH})_2\right]=9 \times 10^{-10}

and

\mathrm{K}_{\mathrm{sp}}\left[\mathrm{B}(\mathrm{OH})_3\right]=27 \times 10^{-18}

at 298 K .

Options

ABoth $\mathrm{A}(\mathrm{OH})_2$ and $\mathrm{B}(\mathrm{OH})_3$ do not show precipitation with $\mathrm{NH}_4 \mathrm{OH}$
B $\mathrm{A}(\mathrm{OH})_2$ will precipitate before $\mathrm{B}(\mathrm{OH})_3$
C $\mathrm{B}(\mathrm{OH})_3$ will precipitate before $\mathrm{A}(\mathrm{OH})_2$
D $\mathrm{A}(\mathrm{OH})_2$ and $\mathrm{B}(\mathrm{OH})_3$ will precipitate together

Correct answer

C. $\mathrm{B}(\mathrm{OH})_3$ will precipitate before $\mathrm{A}(\mathrm{OH})_2$

Step-by-step solution

Condition for precipitation

\mathrm{Q}_{\text{ip }}>\mathrm{K}_{\text{sp }}

For

\left[\mathrm{A}(\mathrm{OH})_2\right]

\begin{aligned} & {\left[\mathrm{A}^{2+}\right][\mathrm{OH}]^2>9 \times 10^{-10}} \\ & {\left[\mathrm{ A}^{+2}\right]=1 \mathrm{M}} \\ & \Rightarrow\left[\mathrm{OH}^{-}\right]>3 \times 10^{-5} \mathrm{M} \end{aligned}

For $\left[\mathrm{B}(\mathrm{OH})_3\right]

\begin{aligned} & {\left[\mathrm{B}^{3+}\right]\left[\mathrm{OH}^{-}\right]^3>27 \times 10^{-18}} \\ & {\left[\mathrm{ B}^{3+}\right]=1 \mathrm{M}} \\ & \Rightarrow\left[\mathrm{OH}^{-}\right]>3 \times 10^{-6} \mathrm{M} \end{aligned}$$

So,

\mathrm{B}(\mathrm{OH})_3

will precipitate before

\mathrm{A}(\mathrm{OH})_2$

Practice Ionic Equilibrium on Quantrex Academy →

More from Ionic Equilibrium

Given is a concentrated solution of a weak electrolyte A_xB_y of concentration 'c' and… JEE Main 2026 M_3 A_2 is a sparingly soluble salt of molar mass y g mol ^ -1 and solubility x g L ^ -1… JEE Main 2026 Arrange the following resultant mixtures in increasing order of their pH values A. 10 mL… JEE Main 2026 20 mL of a solution of acetic acid required 28.4 mL of 0.1 M NaOH for its neutralization.… JEE Main 2026 The pH of a solution obtained by mixing 5 mL of 0.1 M NH_4OH solution with 250 mL of 0.1… JEE Main 2026 The first and second ionization constants of a weak dibasic acid H_2 A are 8.1 × 10^ -8… JEE Main 2026 At 25°C , 20.0 mL of 0.2 M weak monoprotic acid HX is titrated against 0.2 M NaOH. The pH… JEE Main 2026 The solubility product constants of Ag_2CrO_4 and AgBr are 32x and 4y respectively at 298… JEE Main 2026 Full Ionic Equilibrium list All JEE Main PYQs