Salt Analysis

JEE Chemistry · 30 questions · Page 1 of 3 · Click an option or "Show Solution" to reveal answer

Cu2+ salt reacts with potassium iodide to give

A Cu2I2

B Cu2I3

C Cul

D Cu(I3)2

Correct Answer

Option C

Solution

When a copper(II) salt (containing Cu²⁺) is treated with potassium iodide (KI), the cupric ions (Cu²⁺) are reduced to copper(I) (Cu⁺), and iodine (I₂) is released.

The solid product formed in the reaction is copper(I) iodide, CuI.

The simplified reaction is: $\text{2 Cu}^{2+} + 4 \text{I}^{-} \;\longrightarrow\; 2 \,\text{CuI} \!\downarrow + \text{I}_{2}$ So, the correct answer is: Option C: CuI.

To an aqueous solution containing ions such as Al3+, Zn2+, Ca2+, Fe3+, Ni2+, Ba2+ and Cu2+ was added conc. HCl, followed by H2S. The total number of cations precipitated during this reaction is/are :

A 1

B 3

C 4

D 2

Correct Answer

Option A

Solution

Al3+ and Fe3+ sulphides hydrolyse in water.

Ni2+ and Zn2+ require basic medium with H2S to form ppt Ca2+ and Ba2+ sulphides are soluble hence, we will receive only CuS ppt.

A white precipitate was formed when BaCl2 was added to water extract of an inorganic salt. Further, a gas 'X' with characteristic odour was released when the formed white precipitate was dissolved in dilute HCl. The anion present in the inorganic salt is

A I

-

B SO32

-

C S2

-

D NO2

-

Correct Answer

Option B

Solution

Anion is $\mathrm{SO}_{3}^{-2}$

\mathrm{BaSO}_{3} \stackrel{\text{ dil } \mathrm{HCl}}{\longrightarrow} \underset{x(\text{ gas })}{\mathrm{SO}_{2} \uparrow}

Gas is released with smell of burning sulphur.

During halogen test, sodium fusion extract is boiled with concentrated HNO3 to

A remove unreacted sodium

B decompose cyanide or sulphide of sodium

C extract halogen from organic compound

D maintain the pH of extract.

Correct Answer

Option B

Solution

During test for halogen, if nitrogen or sulphur is also present in the compound, then sodium fusion extract is first boiled with concentrated nitric acid to decompose cyanide or sulphide of sodium formed during Lassaigne's test.

In the flame test of a mixture of salts, a green flame with blue centre was observed. Which one of the following cations may be present?

A Cu2+

B Sr2+

C Ba2+

D Ca2+

Correct Answer

Option A

Solution

Cupric salts give green flame with blue centre.

The colour of other salts are $\begin{array}{ll}\mathrm{Sr}^{2+} & \text{ Crimson red } \\ \mathrm{Ca}^{2+} & \text{ Brick red } \\ \mathrm{Ba}^{2+} & \text{ Green }\end{array}$

During the qualitative analysis of salt with cation y2+, addition of a reagent (X) to alkaline solution of the salt gives a bright red precipitate. The reagent (X) and the cation (y2+) present respectively are :

A Dimethylglyoxime and Ni2+

B Dimethylglyoxime and Co2+

C Nessler's reagent and Hg2+

D Nessler's reagent and Ni2+

Correct Answer

Option A

Solution

On addition of dimethylglyoxime to alkaline solution of $\mathrm{Ni}^{+2}$ , a bright red ppt. is obtained.

$\mathrm{Ni}^{+2}+2 \mathrm{dmg} \rightarrow\left[\mathrm{Ni}(\mathrm{dmg})_{2}\right]^{+2}$ (Bright red ppt)

A solution containing a group-IV cation gives a precipitate on passing H2S. A solution of this precipitate in dil.HCl produces a white precipitate with NaOH solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is :

A Co2+

B Ni2+

C Mn2+

D Zn2+

Correct Answer

Option D

Solution

Solution containing Zn2+ ions forms white precipitate on reaction with H2S gas.

A solution of m-chloronailimne, m-chlorophenol and m-chlorobenzoic acid in ethyal acetate was extracted initially with a saturated solution of NaHCO3 to give fraction A. The left over organic phase was extracted with dilute NaoH solution tio give fraction B. The final organiic layer was labelled as fraction C. Fractions A,B and C, contain respectively :

A m-chlorobenzoic acid, m-chloroaniline and m-chlorophenol.

B m-chlorobenzoic acid, m-chlorophenol and m-chloroaniline.

C m-chlorophenol, m-chlorobenzoic acid and m-chloronailine.

D m-chloroaniline m-chlorobenzoic acid and m-chlorophenol.

Correct Answer

Option B

Solution

m-chlorobenzoic acid dissolves in aq NaHCO3 while m-chlorophenol dissolves in aq NaOH.

Given below are two statements : Statement I : The identification of Ni2+ is carried out by dimethyl glyoxime in the presence of NH4OH. Statement II : The dimethyl glyoxime is a bidentate neutral ligand. In the light of the above statements, choose the correct answer from the options given below :

A Statement I is false but Statement II is true.

B Statement I is true but Statement II is false.

C Both Statement I and Statement II are false.

D Both Statement I and Statement II are true.

Correct Answer

Option D

Solution

Statement I is true.

Dimethyl glyoxime (DMG) is a chelating reagent commonly used for the identification of Ni2+ ions in aqueous solution.

In the presence of ammonium hydroxide (NH4OH), Ni2+ reacts with dimethyl glyoxime to form a deep red-colored complex, which can be used to confirm the presence of Ni2+ ions.

Statement II is also true.

Dimethyl glyoxime is a neutral bidentate ligand, which means it has two donor atoms that can coordinate with a metal ion, and its overall charge is neutral.

Q10

In the wet tests for identification of various cations by precipitation, which transition element cation doesn't belong to group IV in qualitative inorganic analysis?

A Co2+

B Ni2+

C Zn2+

D Fe3+

Correct Answer

Option D

Solution

In qualitative inorganic analysis, cations are divided into different groups based on their precipitation reactions.

Group IV cations typically include those that form sulfides or hydroxides that are insoluble in water and dilute acids, but soluble in excess ammonia or sodium hydroxide.

Co $^{2+}$ (Cobalt) Ni $^{2+}$ (Nickel) Zn $^{2+}$ (Zinc) These cations are generally placed in Group IV because they form precipitates with specific reagents used in the separation process.

Fe $^{3+}$ (Iron), on the other hand, is not typically included in Group IV.

It belongs to Group III because it forms insoluble hydroxides that precipitate in the presence of ammonia.

Thus, the transition element cation that doesn't belong to Group IV is: Option D Fe $^{3+}$

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