A mixture of two salts is used to prepare a solution $\mathbf{S}$, which gives the following results: $\underset{\text{only}}{\text{White}}$ precipitate(s) $\xleftarrow[\text{Room temperature}]{\text{Dilute NaOH(aq.)}}$ $\underset{\text{(aq. solution)}}{\mathbf{S}\text{ of the salts})}$ $\xrightarrow[\text{Room temperature}]{\text{Dilute HCl(aq.)}}$ $\underset{\text{only}}{\text{White}}$ precipitate(s) The correct option(s) for the salt mixture is(are)

(A) $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$ and $\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}$; (B) $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$ and $\mathrm{Bi}\left(\mathrm{NO}_{3}\right)_{3}$

(C) $\mathrm{AgNO}_{3}$ and $\mathrm{Bi}\left(\mathrm{NO}_{3}\right)_{3}$

(D) $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$ and $\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2}$

JEE Advanced · 2021 · 03 Oct 2021 · Paper 1 · Practical and Analytical Chemistry

WhatsApp Email

A mixture of two salts is used to prepare a solution

S

, which gives the following results:

only White

precipitate(s)

Dilute NaOH(aq.) Room temperature

(aq. solution) S of the salts)

Dilute HCl(aq.) Room temperature

only White

precipitate(s)
The correct option(s) for the salt mixture is(are)

(A) $Pb (NO_{3})_{2}$ and $Zn (NO_{3})_{2}$ ✓ Correct
(B) $Pb (NO_{3})_{2}$ and $Bi (NO_{3})_{3}$ ✓ Correct
(C) $AgNO_{3}$ and $Bi (NO_{3})_{3}$
(D) $Pb (NO_{3})_{2}$ and $Hg (NO_{3})_{2}$

Answer: (A), (B)

Solution

A white precipitate with dilute

HCl

requires an insoluble chloride such as

P b^{2 +}

(giving

PbC l_{2}

) or

A g^{+}

(giving

AgCl

); a white precipitate with dilute

NaOH

requires a white hydroxide such as

Pb (OH)_{2}

Zn (OH)_{2}

Bi (OH)_{3}

. The mixture of

Pb (N O_{3})_{2}

and

Zn (N O_{3})_{2}

gives white

PbC l_{2}

with

HCl

and white

Pb (OH)_{2}

and

Zn (OH)_{2}

with

NaOH

, and

Pb (N O_{3})_{2}

with

Bi (N O_{3})_{3}

gives white

PbC l_{2}

and white

Pb (OH)_{2}

and

Bi (OH)_{3}

; both satisfy the test. The

AgN O_{3}

and

Bi (N O_{3})_{3}

mixture does not, because

A g^{+}

with

NaOH

gives brown

A g_{2} O

rather than a white precipitate.

JEE Advanced · 2021 · 03 Oct 2021 · Paper 1 · One or more correct options

Practise more: all JEE Advanced PYQs on Practical and Analytical Chemistry →

JEE Advanced · 2021 · 03 Oct 2021 · Paper 1 · Practical and Analytical Chemistry

Solution

More JEE Advanced questions on Practical and Analytical Chemistry