Salt Analysis — Page 3 | JEE Chemistry

Q21

Given below are two statements : Statement I : Mohr's salt is composed of only three types of ions-ferrous, ammonium and sulfate. Statement II : If the molar conductance at infinite dilution for ferrous, ammonium and sulfate ions are

x_1, x_2

and

x_3 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}

, respectively then the molar conductance for Mohr's salt solution at infinite dilution would be given by

x_1+x_2+2 x_3

In the light of the given statements, choose the correct answer from the options given below :

A Both Statements I and Statement II are true

B Statement I is true but Statement II are false

C Both Statements I and Statement II are false

D Statement I is false but Statement II is true

Correct Answer

Option B

Solution

Mohr's salt is chemically represented as $\mathrm{FeSO}_4 \cdot\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4 \cdot 6 \mathrm{H}_2 \mathrm{O}$ .

To understand its composition, Mohr's salt dissociates into the following ions: Fe $^ {2+}$ (ferrous ion) 2 NH $_4^+$ (ammonium ions) 2 SO $_4^{2-}$ (sulfate ions) Thus, Mohr's salt contains ferrous, ammonium, and sulfate ions, but also has water molecules that hydrate these ions.

Using Kohlrausch's Law of independent ionic mobility, the molar conductance at infinite dilution for an electrolyte is the sum of the ionic conductances of its constituent ions: $\lambda_{\mathrm{m}}^{\infty}(\text{Mohr's salt}) = \mathrm{x}_1 + 2\mathrm{x}_2 + 2\mathrm{x}_3$ Here: $x_1$ represents the molar conductance of the ferrous ion (Fe $^ {2+}$ ), $x_2$ represents the molar conductance of the ammonium ion (NH $_4^+$ ), $x_3$ represents the molar conductance of the sulfate ion (SO $_4^{2-}$ ).

Therefore, statement II should include the correct expression $x_1 + 2x_2 + 2x_3$ to accurately describe the molar conductance for Mohr's salt.

Q22

When a salt is treated with sodium hydroxide solution it gives gas X . On passing gas X through reagent Y a brown coloured precipitate is formed. X and Y respectively, are

A

\mathrm{X}=\mathrm{NH}_3

and

\mathrm{Y}=\mathrm{HgO}

B

\mathrm{X}=\mathrm{NH}_4 \mathrm{Cl}

and

\mathrm{Y}=\mathrm{KOH}

C

\mathrm{X}=\mathrm{NH}_3

and

\mathrm{Y}=\mathrm{K}_2 \mathrm{HgI}_4+\mathrm{KOH}

D

\mathrm{X}=\mathrm{HCl}

and

\mathrm{Y}=\mathrm{NH}_4 \mathrm{Cl}

Correct Answer

Option C

Solution

$\mathrm{NH}_3$ is identify by $\mathrm{K}_2\left[\mathrm{HgI}_4\right]+\mathrm{KOH}$

Q23

Formation of

\mathrm{Na}_4\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NOS}\right]

, a purple coloured complex formed by addition of sodium nitroprusside in sodium carbonate extract of salt indicates the presence of :

A Sulphide ion

B Sulphite ion

C Sulphate ion

D Sodium ion

Correct Answer

Option A

Solution

$\underset{\substack{\text{ Sodium } \\ \text{ sulphide }}}{\mathrm{Na}_2 \mathrm{S}}+\underset{\substack{\text{ Sodium nitro } \\ \text{ Prusside }}}{\mathrm{Na}_2\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NO}\right]}\rightarrow \underset{\substack{\text{ Violet Colour } \\ }}{\mathrm{Na}_4\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NOS}\right]}$

Q24

Compounds that should not be used as primary standards in titrimetric analysis are : A.

\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7

B. Oxalic acid C. NaOH D.

\mathrm{FeSO}_4 \cdot 6 \mathrm{H}_2 \mathrm{O}

E. Sodium tetraborate Choose the most appropriate answer from the options given below:

A C, D and E Only

B B and D Only

C D and E Only

D A, C and D Only

Correct Answer

Option D

Solution

The primary standard is a highly pure stable compound with a known exact composition that can be accurately weighed and dissolved to creat a solution of known concentration. $\mathrm{NaOH}$ is hygroscopic and can't be used. $\mathrm{FeSO}_4 \cdot 6 \mathrm{H}_2 \mathrm{O}$ is unstable and can be easily oxidised. $\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7$ is hygroscopic and can't be used.

Q25

Match the following : .tg .tg Test/Method Reagent

List - I		List - II
(a)	C6H5SO2Cl/ aq. KOH	(i)	Lucas Test
(b)	HNO3/ AgNO3	(ii)	Dumas method
(c)	CuO/CO2	(iii)	Kjeldahl’s method
(d)	Conc. HCl and ZnCl2 (e) H2SO4	(iv)	Hinsberg test

A (i)-(b), (ii)-(d), (iii)-(e), (iv)-(a)

B (i)-(d), (ii)-(c), (iii)-(e), (iv)-(a)

C (i)-(b), (ii)-(a), (iii)-(c), (iv)-(d)

D (i)-(d), (ii)-(c), (iii)-(b), (iv)-(e)

Correct Answer

Option B

Solution

Lucas reagent – Conc. HCl/ZnCl2 Dumas method – CuO/CO2 Kjeldahl’s method – H2SO4 Hinsberg test – C6H5SO2Cl/aq. KOH

Q26

Match the LIST-I with LIST-IILIST-I (Reagent)LIST-II (Functional Group detected)A. Sodium bicarbonate solutionI. double bond/unsaturationB. Neutral ferric chlorideII. carboxylic acidC. ceric ammonium nitrateIII. phenolic - OHD. alkaline KMnO4IV. alcoholic - OHChoose the correct answer from the options given below:

A A-II, B-III, C-I, D-IV

B A-II, B-IV, C-III, D-I

C A-III, B-II, C-IV, D-I

D A-II, B-III, C-IV, D-I

Correct Answer

Option D

Solution

(1) Carboxylic acid gives efferve scence with sodium bicarbonate solution (2) Phenolic-OH gives voilet coloured complex with Neutral $\mathrm{FeCl}_3$ .

(3) Alcoholic-OH gives Red colour with cerric ammonium Nitrate.

(4) When alkaline $\mathrm{KMnO}_4$ reacts with an unsaturated compound (Alkene or alkyne) the purple colour of $\mathrm{KMnO}_4$ solution disappears, indicating positive test for unsaturation.

Q27

Match List I with List II .tg .tg LIST I (Name of the test) LIST II (Reaction sequence involved) [M is metal] A. Borax bead test I.

\mathrm{MCO}_3 \rightarrow \mathrm{MO} \xrightarrow[+\Delta]{\mathrm{Co}\left(\mathrm{NO}_3\right)_2} \mathrm{CoO} \cdot \mathrm{MO}

B. Charcoal cavity test II.

\mathrm{MCO}_3 \rightarrow \mathrm{MCl}_2 \rightarrow \mathrm{M}^{2+}

C. Cobalt nitrate test III.

\mathrm{MSO}_4 \xrightarrow[\Delta]{\mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7} \mathrm{M}\left(\mathrm{BO}_2\right)_2 \rightarrow \mathrm{MBO}_2 \rightarrow \mathrm{M}

D. Flame test IV.

\mathrm{MSO}_4 \xrightarrow[\Delta]{\mathrm{Na}_2 \mathrm{CO}_3} \mathrm{MCO}_3 \rightarrow \mathrm{MO} \rightarrow \mathrm{M}

Choose the correct answer from the options given below:

A A-III, B-I, C-IV, D-II

B A-III, B-IV, C-I, D-II

C A-III, B-II, C-IV, D-I

D A-III, B-I, C-II, D-IV

Correct Answer

Option B

Solution

(A) Borax bead test

\mathrm{MSO}_4 \xrightarrow[\Delta]{\mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7} \mathrm{M}\left(\mathrm{BO}_2\right)_2 \rightarrow \mathrm{MBO}_2 \rightarrow \mathrm{M}

(B) Charcoal cavity test

\mathrm{MSO}_4 \xrightarrow[\Delta]{\mathrm{Na}_2 \mathrm{CO}_3} \mathrm{MCO}_3 \rightarrow \mathrm{MO} \rightarrow \mathrm{M}

(C) Cobalt nitrate test

\mathrm{MCO}_3 \rightarrow \mathrm{MO} \xrightarrow[+\Delta]{\mathrm{CO}\left(\mathrm{NO}_3\right)_2} \mathrm{CoO} \cdot \mathrm{MO}

(D) Flame test

\mathrm{MCO}_3 \rightarrow \mathrm{MCl}_2 \rightarrow \mathrm{M}^{2+}

So,

\mathrm{A} \rightarrow

(III),

\mathrm{B} \rightarrow

(IV),

\mathrm{C} \rightarrow

(I),

\mathrm{D} \rightarrow

(II).

Q28

Match List I with List II .tg .tg LIST I (Precipitating reagent and conditions) LIST II (Cation) A.

\mathrm{NH}_4 \mathrm{Cl}+\mathrm{NH}_4 \mathrm{OH}

I.

\mathrm{Mn^{2+}}

B.

\mathrm{NH}_4 \mathrm{OH}+\mathrm{Na}_2 \mathrm{CO}_3

II.

\mathrm{Pb^{2+}}

C.

\mathrm{NH}_4 \mathrm{OH}+\mathrm{NH}_4 \mathrm{Cl}+\mathrm{H}_2 \mathrm{~S} \text{ gas }

III.

\mathrm{Al^{3+}}

D. dilute

\mathrm{HCl}

IV.

\mathrm{Sr^{2+}}

Choose the correct answer from the options given below:

A A-III, B-IV, C-I, D-II

B A-III, B-IV, C-II, D-I

C A-IV, B-III, C-II, D-I

D A-IV, B-III, C-I, D-II

Correct Answer

Option A

Solution

\begin{array}{lll} \mathrm{A} & \rightarrow \mathrm{Al}^{3+}(\mathrm{III}) \\ \mathrm{B} & \rightarrow \mathrm{Sr}^{2+}(\mathrm{IV}) \\ \mathrm{C} & \rightarrow \mathrm{Mn}^{2+}(\mathrm{I}) \\ \mathrm{D} & \rightarrow \mathrm{Pb}^{2+}(\mathrm{II}) \end{array}

Q29

Match List I with List II .tg .tg List I Elements List II Colour imparted to the flame A. K I. Brick Red B. Ca II. Violet C. Sr III. Apple Green D. Ba IV. Crimson Red Choose the correct answer from the options given below :

A A-II, B-IV, C-I, D-III

B A-II, B-I, C-IV, D-III

C A-II, B-I, C-III, D-IV

D A-IV, B-III, C-II, D-I

Correct Answer

Option B

Solution

.tg .tg Element $\begin{aligned} & \text{ Colour imparted to } \\ & \text{ the flame }\end{aligned}$ (A) $\mathrm{K}$ Violet (B) $\mathrm{Ca}$ Brick red (C) $\mathrm{Sr}$ Crimson red (D) $\mathrm{Ba}$ Apple green

Q30

Match the List-I with List-II : .tg .tg List-I Cations List-II Group reagents A.

\mathrm{Pb^{2+},Cu^{2+}}

i)

\mathrm{H_2S}

gas in presence of dilute HCl B.

\mathrm{Al^{3+},Fe^{3+}}

ii)

\mathrm{(NH_4)_2CO_3}

in presence of

\mathrm{NH_4OH}

C.

\mathrm{Co^{2+},Ni^{2+}}

iii)

\mathrm{NH_4OH}

in presence of

\mathrm{NH_4Cl}

D.

\mathrm{Ba^{2+},Ca^{2+}}

iv) H2S in presence of NH4OH Correct match is -

A A

\to

i, B

\to

iii, C

\to

iv, D

\to

ii

B A

\to

i, B

\to

iii, C

\to

ii, D

\to

iv

C A

\to

iii, B

\to

i, C

\to

iv, D

\to

ii

D A

\to

iv, B

\to

ii, C

\to

iii, D

\to

i

Correct Answer

Option A

Solution

.tg .tg Cations Group No.

Group reagent $\mathrm{Pb}^{+2}, \mathrm{Cu}^{+2}$ II $\mathrm{H}_2 \mathrm{S}(\mathrm{g}) \text{ in presence of } \text{ dil HCl }$ $\mathrm{Al}^{+3}, \mathrm{Fe}^{+3}$ III $\begin{aligned} & \mathrm{NH}_4 \mathrm{OH} \text{ in presence of } \\ & \mathrm{NH}_4 \mathrm{Cl}\end{aligned}$ $\mathrm{CO}^{+2}, \mathrm{Ni}^{+2}$ $\mathrm{IV}$ $\begin{aligned} & \mathrm{H}_2 \mathrm{~S} \text{ in presence of } \\ & \mathrm{NH}_4 \mathrm{OH}\end{aligned}$ $\mathrm{Ba}^{+2}, \mathrm{Ca}^{+2}$ $\mathrm{~V}$ $\begin{aligned} & \left(\mathrm{NH}_4\right)_2 \mathrm{CO}_3 \text{ in presence } \\ & \text{ of } \mathrm{NH}_4 \mathrm{OH}\end{aligned}$