Embibe Experts Solutions for Chapter: Qualitative Analysis, Exercise 4: EXERCISE-4

A mixture of three gases $\mathrm{A},\mathrm{B}$ and $\mathrm{C}$ is passed first into acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ solution when $\mathrm{A}$ is absorbed turnign the solution green. The remainder of the gas is passed through excess of lime water which turns milky resulting in the absorption of $\mathrm{B}$. The residual gas $\mathrm{C}$ is absorbed by alkaline pyrogallol solution. However the original mixture does not turn lead acetate paper black. Identify $\mathrm{A},\mathrm{B}$ & $\mathrm{C}$ (Give necessary equations).

An unknown inorganic compound $\left(\mathrm{X}\right)$ loses its water of crystallisation. On heating its aqueous solution gives the following reaction:

(i) It gives a white turbidity with dilute $\mathrm{HCl}$ solution.

(ii) It decolourises a solution of iodine in $\mathrm{KI}$.

(iii) It gives a white precipitate with ${\mathrm{AgNO}}_3$ solution which turns black on standing.

Identify compound $\left(\mathrm{X}\right)$ and give chemical equations for the reactions at step (i), (ii) & (iii).

An inorganic compound $\left(\mathrm{X}\right)$ gives brick red flame on performing the flame test. This also give the following tests:

(i) Smell of chlorine when placed in moist air.

(ii) If $\mathrm{KI}$ & ${\mathrm{CH}}_3\mathrm{COOH}$ are added to its suspension in water, a brown colour is obtained. Identify $\left(\mathrm{X}\right)$ and write down equations for reactions at step (i) and (ii).

Two solid laboratory reagents $\left(\mathrm{A}\right)$ and $\left(\mathrm{B}\right)$ give following reactions:

Compound: $\left(\mathrm{A}\right)$

(i) On strongly heating it gives two oxides of sulphur.

(ii) On adding aqueous $\mathrm{NaOH}$ solution to its aqueous solution, a dirty green precipitate is obtained which starts turning brown on exposure to air.

Compound: $\left(\mathrm{B}\right)$

(iii) It imparts green colour to flame.

(iv) Its solution doesn't give precipitate on passing ${\mathrm{H}}_2\mathrm{S}$

(v) When it is heated with ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ & conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$, a red gas is evolved. The gas when passed in aqueous $\mathrm{NaOH}$ solution turns it yellow.

Identify $\left(\mathrm{A}\right)$ to $\left(\mathrm{B}\right)$ and give chemical reactions.

On mixing the aqueous solutions of compounds $\left(\mathrm{A}\right)$ and $\left(\mathrm{B}\right)$, an insoluble compound $\left(\mathrm{C}\right)$ is produced along with another water soluble compound $\left(\mathrm{D}\right)$. Compound $\left(\mathrm{A}\right)$ and $\left(\mathrm{B}\right)$, an insoluble compound $\left(\mathrm{C}\right)$ is produced along with another water soluble compound $\left(\mathrm{D}\right)$. Compound $\left(\mathrm{A}\right)$ on heating gives brown ${\mathrm{NO}}_2$ gas with a cracking noise. An aqueous solution of compound $\left(\mathrm{A}\right)$ gives black ppt. With ${\mathrm{H}}_2\mathrm{S}$ gas. Compound $\left(\mathrm{A}\right)$ also gives white ppt. with dil. $\mathrm{HCl}$ which is soluble in hot water and reappears on cooling. The hot water extract of compound $\left(\mathrm{A}\right)$ gives yellow ppt. with ${\mathrm{K}}_2{\mathrm{CrO}}_4$ solution.

A black coloured compound $\left(\mathrm{A}\right)$ on reaction with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$ gives a gas $\left(\mathrm{B}\right)$ which on passing in a solution of an acid $\left(\mathrm{C}\right)$ gives a white turbidity $\left(\mathrm{D}\right)$. Gas $\left(\mathrm{B}\right)$ when passed in an acidified solution of a compound $\left(\mathrm{E}\right)$ gives a precipitate $\left(\mathrm{F}\right)$ soluble in dil ${\mathrm{HNO}}_3$. After boiling this solution when an excess of ${\mathrm{NH}}_4\mathrm{OH}$ is added, a blue coloured compound $\left(\mathrm{G}\right)$ is formed. To this solution on addition of acetic acid and aqueous ${\mathrm{K}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$ a chocolate precipitate $\left(\mathrm{H}\right)$ is obtained. On addition of an aqueous solution of ${\mathrm{BaCl}}_2$to an aqueous solution of $\left(\mathrm{E}\right)$, a white  precipitate insoluble in ${\mathrm{HNO}}_3$ is obtained. Identify $\left(\mathrm{A}\right)$ to $\left(\mathrm{H}\right)$. 

An aqueous solution of an unknown compound $\left(\mathrm{X}\right)$ gives the following reactions.

(i) It gives brown precipitate with alkaline ${\mathrm{KMnO}}_4$ solution

(ii) It forms $\mathrm{HCl}$ & evolved ${\mathrm{O}}_2$ when reacts with ${\mathrm{Cl}}_2$ gas.

(iii) It liberates ${\mathrm{I}}_2$ from an acidified $\mathrm{KI}$ solution.

(iv) It gives orange yellow colour with acidified titanic sulphate solution.

Identify $\left(\mathrm{X}\right)$ and give the chemical equations for the reactions (i), (ii) & (iii). 

A metal chloride $\left(\mathrm{X}\right)$ shows the following reactions:

(i) When ${\mathrm{H}}_2\mathrm{S}$ is passes in an acidified aqueous solution of $\left(\mathrm{X}\right)$ a black ppt is a obtained.

(ii) The precipitate obtained in step (i) is not soluble in yellow ammonium sulphide.

(iii) When a solution of stannous chloride is added to an aqueous solution of $\left(\mathrm{X}\right)$,a white precipitate is obtained which turns grey on addition of more of stannous chloride.

(iv) When an aqueous solution of $\mathrm{KI}$ is added to an aqueous solution of $\left(\mathrm{X}\right)$, a red precipitate is obtained which dissolves on addition of excess of $\mathrm{KI}$.

Identify $\left(\mathrm{X}\right)$ and write down the equations for the reaction at steps (i), (iii) & (iv).