Qualitative Analysis - Result Question 49
####52. A salt mixture consists of a yellow solid $(A)$ and a colourless solid $(B)$. The aqueous solution of the mixture
(i) On passing $H _2 S$, we get a black precipitate of $(C)$, which dissolves only in aqua-regia. On extraction and reaction with $SnCl _2$ a greyish white precipitate is obtained.
(ii) On treatment with ammonium hydroxide a reddish brown precipitate $(D)$ is obtained.
The sodium extract of the solution gives the following tests:
(i) On reaction with $AgNO _3$ it gives a yellow precipitate which is insoluble in $NH _3$.
(ii) On shaking with $FeCl _3$ and $CCl _4$ a violet colouration in $CCl _4$ layer is obtained. Mixture on performing flame test gives lilac colour. Identify the compounds $(A),(B),(C)$ and $(D)$.
(2003)
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Solution:
- $\underbrace{A+B} _{\text {Mixture }} \longrightarrow$ lilac colour in flame
(i) $\underbrace{A+B} _{\text {Mixture }} \xrightarrow{H _2 S} \underset{\text { Black }}{C \downarrow}$
$C \xrightarrow[\text { in aqua-regia }]{\text { Soluble }}$ Soluble $\xrightarrow{\text { Evaporation }}$ Residue
$\xrightarrow{SnCl _2}$ Greyish black $\downarrow(D)$
$\Rightarrow \quad C$ is $HgS$. (ii) $\underbrace{A+B} _{\begin{array}{c}\text { Solution of } \ \text { mixture }\end{array}} \xrightarrow{NH _4 OH}$ Brown ppt.
Sodium extract $\xrightarrow{AgNO _3}$ Yellow ppt. $\xrightarrow{NH _3}$ Insoluble Sodium extract of salt $\xrightarrow{CCl _4 / FeCl _3}$ Violet layer $\Rightarrow \quad A=KI$ and $B=HgI _2$.
