Question

What is the product obtained when $MnS{O_4}$ solution is boiled with $Pb{O_2}$ and concentrated $HN{O_3}$ ?
(A) $Mn{O_2}$
(B) $HMn{O_4}$
(C) $M{n_3}{O_4}$
(D)$PbMn{O_4}$

Answer 1

Permanganic acid is the conjugate acid of permanganate salts. It is most often prepared by the reaction of dilute sulphuric acid with a solution of barium permanganate. It is an inorganic acid that exists only in dilute solution and is unstable. Its purple aqueous solution is known to be used as an oxidizing agent.

Complete answer:
When $MnS{O_4}$ solution is boiled with $Pb{O_2}$ and concentrated $HN{O_3}$ we get permanganic acid ($HMn{O_4}$), lead sulphate($PbS{O_4}$) and lead nitrate ($Pb{(N{O_3})_2}$.
$2MnS{O_4} + 5Pb{O_2} + 6HN{O_3} \to 2HMn{O_4} + 2PbS{O_4} + 3Pb{(N{O_3})_2} + 2{H_2}O$

Hence, the correct option is (B) $HMn{O_4}$ .

Additional information:
Permanganic acid is a strong oxoacid and it has been isolated as its dihydrate. Crystalline permanganic acid has been prepared at low temperatures as its dihydrate. It is a strong acid. As a strong acid, it is deprotonated to form the intensely purple-coloured permanganates. Permanganic acid solutions are unstable and dissolve slowly into manganese dioxide, oxygen, and water, with the manganese dioxide that forms first catalysing further decomposition. Heat, light, and acids speed up the decomposition process. Concentrated solutions degrade faster than dilute solutions.

Note:
The sulphuric acid used must be dilute in reactions where permanganic acid is produced. The reaction of permanganates with concentrated sulphuric acid yields anhydride. Permanganic acid is a conjugate acid of permanganate salts.