Ionic Equilibrium | JEE Main Chemistry Chapter Wise Question Papers

Q 1 :

Consider two Group IV metal ions $X^{2 +}$ and $Y^{2 +}$ .

A solution containing $0.01 M X^{2 +}$ and $0.01 M Y^{2 +}$ is saturated with $H_{2} S$ . The pH at which the metal sulphide YS will form as a precipitate is ________. (Nearest integer)

(Given: $K_{s p} (X S) = 1 \times 10^{- 22}$ at $25 ° C,$ $K_{s p} (Y S) = 4 \times 10^{- 16}$ at $25 ° C,$

$[H_{2} S] = 0.1 M in solution, K_{a 1} \times K_{a 2} (H_{2} S) = 1.0 \times 10^{- 21},$ $\log 2 = 0.30, \log 3 = 0.48, \log 5 = 0.70$ ) [2026]

(4)

$XS (s) ⇌ X^{2 +} (aq) + S^{2 -} (aq)$

$For precipitation of XS(s)$

$[X^{2 +}] [S^{2 -}] \geq K_{s p} (XS)$

$[S^{2 -}] \geq \frac{1 \times 10^{- 22}}{0.01} = 10^{- 20}$

$YS (s) ⇌ Y^{2 +} (aq) + S^{2 -} (aq)$

$For precipitation of YS(s)$

$[Y^{2 +}] [S^{2 -}] \geq K_{s p} (YS)$

$[S^{2 -}] \geq \frac{4 \times 10^{- 16}}{10^{- 2}} = 4 \times 10^{- 14}$

$Now, H_{2} S (aq) ⇌ 2 H^{+} (aq) + S^{2 -} (aq)$

$\frac{[S^{2 -}] {[H^{+}]}^{2}}{[H_{2} S]} = K_{a 1} \times K_{a 2} = 1 \times 10^{- 21}$

$[S^{2 -}] = \frac{1 \times 10^{- 21} \times [H_{2} S]}{{[H^{+}]}^{2}} \geq 4 \times 10^{- 14}$

${[H^{+}]}^{2} \leq \frac{1}{4} \times 10^{- 7} \times 10^{- 1}$

$[H^{+}] \leq \frac{1}{2} \times 10^{- 4} \Rightarrow pH \geq 4.3$

Q 2 :

The first and second ionization constants of $H_{2} X$ are $2.5 \times 10^{- 8}$ and $1.0 \times 10^{- 13}$ respectively. The concentration of $X^{2 -}$ in $0.1 M H_{2} X$ solution is______ $\times 10^{- 15} M$ . (Nearest Integer) [2026]

(100)

$\begin{matrix} H_{2} X & ⇌ & H^{+} & + & {HX}^{-} \\ 0.1 - x & x + y & x - y \end{matrix}$

$2.5 \times 10^{- 8} = \frac{(x + y) (x - y)}{0.1 - x}$

$\begin{matrix} {HX}^{-} & ⇌ & H^{+} & + & X^{2 -} \\ x - y & x + y & y \end{matrix}$

$1 \times 10^{- 13} = \frac{(x + y) (y)}{x - y}$

$Approximate : K_{a 1} ≫ K_{a 2} \Rightarrow So x ≫ y$

$x + y \approx x, x - y \approx x$

$10^{- 13} = \frac{x \cdot y}{x}$

$y = 10^{- 13}$

$[X^{2 -}] = 10^{- 13}$

$[X^{2 -}] = 100 \times 10^{- 15}$

Q 3 :

Consider the following statements:

A) ${BF}_{3}$ does not have a proton but still acts as an acid

B) Strong acids have very strong conjugate bases

C) Stronger acid donates a proton to the stronger base

Incorrect statement(s) is/are:

(A) only
(B) only
(A) and (B) only
(A) and (C) only

1

2

3

4

(2)

Q 4 :

100 mL of 0.5 M ${Na}_{3} {PO}_{4}$ aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: $K_{a_{1}}, K_{a_{2}}, K_{a_{3}}$ of $H_{3} {PO}_{4}$ are $10^{- 3}, 10^{- 5}$ and $10^{- 7}$ respectively)

6
4
3.5
4.7

1

2

3

4

(2)

Hint: m. moles of ${Na}_{3} {PO}_{4} = 50$

M moles of HCl = 100

Final solution will have ${NaH}_{2} {PO}_{4}$ (amphoteric salt)

$∴$ $pH = \frac{p K_{a 1} + p K_{a 2}}{2} = 4$

Topic Question Set

Q 2 :

The first and second ionization constants of $H_{2} X$ are $2.5 \times 10^{- 8}$ and $1.0 \times 10^{- 13}$ respectively. The concentration of $X^{2 -}$ in $0.1 M H_{2} X$ solution is______ $\times 10^{- 15} M$ . (Nearest Integer) [2026]

Q 3 :

Consider the following statements:

A) ${BF}_{3}$ does not have a proton but still acts as an acid

B) Strong acids have very strong conjugate bases

C) Stronger acid donates a proton to the stronger base

Incorrect statement(s) is/are:

(2)

Q 4 :

100 mL of 0.5 M ${Na}_{3} {PO}_{4}$ aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: $K_{a_{1}}, K_{a_{2}}, K_{a_{3}}$ of $H_{3} {PO}_{4}$ are $10^{- 3}, 10^{- 5}$ and $10^{- 7}$ respectively)

Want Us to Email you About Special Offers & Updates?

Topic Question Set

Q 2 : The first and second ionization constants of H2X are 2.5×10-8 and 1.0×10-13 respectively. The concentration of X2- in 0.1 M H2X solution is______×10-15 M. (Nearest Integer) [2026]

Q 3 : Consider the following statements: A) BF3 does not have a proton but still acts as an acid B) Strong acids have very strong conjugate bases C) Stronger acid donates a proton to the stronger base Incorrect statement(s) is/are:

(2)

Q 4 : 100 mL of 0.5 M Na3PO4 aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: Ka1, Ka2, Ka3 of H3PO4 are 10-3, 10-5 and 10-7 respectively)

Want Us to Email you About Special Offers & Updates?

Q 2 :

The first and second ionization constants of $H_{2} X$ are $2.5 \times 10^{- 8}$ and $1.0 \times 10^{- 13}$ respectively. The concentration of $X^{2 -}$ in $0.1 M H_{2} X$ solution is______ $\times 10^{- 15} M$ . (Nearest Integer) [2026]

Q 3 :

Consider the following statements:

A) ${BF}_{3}$ does not have a proton but still acts as an acid

B) Strong acids have very strong conjugate bases

C) Stronger acid donates a proton to the stronger base

Incorrect statement(s) is/are:

Q 4 :

100 mL of 0.5 M ${Na}_{3} {PO}_{4}$ aqueous solution is mixed with 80 mL of 1.25 M HCl solution. The pH of the final solution is (Given: $K_{a_{1}}, K_{a_{2}}, K_{a_{3}}$ of $H_{3} {PO}_{4}$ are $10^{- 3}, 10^{- 5}$ and $10^{- 7}$ respectively)