Qualitative Analysis - Result Question 73
####76. What happen when
(i) hydrogen sulphide is bubbled through an aqueous solution of sulphur dioxide.
(ii) aqueous ammonia is added dropwise to a solution of copper sulphate till it is in excess.
(iii) tin is treated with concentrated nitric acid.
(iv) $CrCl _3$ solution is treated with sodium hydroxide and then with hydrogen peroxide.
(v) $Pb _3 O _4$ is treated with nitric acid.
$(1985,5 M)$
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Solution:
- (i) $SO _2+2 H _2 S \longrightarrow 3 S+2 H _2 O$
(ii) $CuSO _4+4 NH _3 \longrightarrow\left[Cu\left(NH _3\right) _4\right] SO _4$ (iii) $Sn+\underset{\text { Conc. }}{3 HNO _3} \longrightarrow \underset{\substack{\text { Metastannic } \ \text { acid }}}{H _2 SnO _3}+4 NO _2+H _2 O$
(iv) $H _2 O _2+CrCl _3+NaOH \longrightarrow \underset{\text { Yellow }}{Na _2 CrO _4}+NaCl+H _2 O$
(v) $Pb _3 O _4 \longrightarrow 2 PbO+PbO _2$
$2 PbO+PbO _2+4 HNO _3 \longrightarrow 2 Pb\left(NO _3\right) _2+2 H _2 O+PbO _2 \downarrow$
