Qualitative Analysis - Result Question 34
####35. Reagent $S$ is
(a) $K _4\left[Fe(CN) _6\right]$
(b) $Na _2 HPO _4$
(c) $K _2 CrO _4$
(d) $KOH$
Passage 2
An aqueous solution of a mixture of two inorganic salts, when treated with dilute $HCl$, gave a precipitate $(P)$ and filtrate $(Q)$. The precipitate $(P)$ was found to dissolve in hot water. The filtrate $(Q)$ remained unchanged, when treated with $H _2 S$ in a dilute mineral acid medium. However, it gave a precipitate $(R)$ with $H _2 S$ in an ammoniacal medium. The precipitate $R$ gave a coloured solution $(S)$, when treated with $H _2 O _2$ in an aqueous $NaOH$ medium.
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Answer:
Correct Answer: 35. $(b, c)$
Solution:
- $Zn^{2+}$ on treatment with excess of $KOH$ produces $\left[Zn(OH) _4\right]^{2-}$.
36, 37. PLAN $PbCl _2$ is soluble in hot water.
In ammoniacal medium, cations of group III and IV may be precipitated as hydroxide or sulphide and dissolved in $H _2 O _2$ due to oxidation.
$$ \text { Mixture of two inorganic salts } \xrightarrow[\text { (ii) Filter }]{\text { (i) } HCl} $$
Thus, Q. 35. $P$ is $Pb^{2+}$. Q. 36. $S$ is $Na _2 CrO _4$.
