Question

Write the following reaction

(a) Dissolution of CuS precipitate in dil.$HNO-3$
$3CuS+8HN{O}_3⟶3Cu(N{O}_3{)}_2+2NO+4H_{2}O+3H_{2}O$

(b) Dissolution of HgS precipitate in aqua regia
$3HgS+2\left(\underset{aquaregia}{HN{O}_3+3HCl}\right)\stackrel{△}{⟶}3HgC{l}_2+2NO+3S$

(c) Dissolution of $A{g}_2{S}_3$ in aqueous NaOH
$A{s}_2{S}_3+6NaOH⟶N{a}_{3}As{O}_3+N{a}_{3}As{S}_3+3H_{2}O+4H_{2}O$

(d) Stannite $\left[Sn\right(OH{)}_3{]}^{-}$ ion disproportionate on long exposure to air
$2\left[Sn\right(OH{)}_3{]}^{-}\to Sn\left(s\right)+\left[Sn\right(OH{)}_6{]}^{2-}$

Which of the given reactions are false?

• A. (a) and (b)
• B. (b) and (c)
• C. (a) and (c)
• D. None of these

Answer 1

The correct option is D None of these

(a)Copper sulphide reacts with dil nitric acid to form soluble copper nitrate.
$3CuS+8HN{O}_3⟶3Cu(N{O}_3{)}_2+2NO+4H_{2}O+3H_{2}O$
(b) Mercuric sulphide reacts with aqua regia to form soluble mercuric sulphide.
$3HgS+2\left(\underset{aquaregia}{HN{O}_3+3HCl}\right)\stackrel{△}{⟶}3HgC{l}_2+2NO+3S$
(c) Arsenic sulphide reacts with sodium hydroxide to form soluble $N{a}_{3}As{O}_{3}andN{a}_{3}As{S}_3$
$A{s}_2{S}_3+6NaOH⟶N{a}_{3}As{O}_3+N{a}_{3}As{S}_3+3H_{2}O+4H_{2}O$
(d) The disproportionation reaction is $2\left[Sn\right(OH{)}_3{]}^{-}\to Sn\left(s\right)+\left[Sn\right(OH{)}_6{]}^{2-}$
In this reaction, tin (II) is reduced to tine(0) and oxidized to Sn(IV).