Pyrolusite on heating with $K O H$ in presence of air gives a dark green compound (A). The solution of (A) on treatment with sulphuric acid gives a purple colour compound (B). Compound (B) with concentrated $H_{2} S O_{4}$ gives (C) which can decompose to (D) and $O_{2}$ . What is the number of unpaired electrons in the cation of (D)?

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Solution

The cation in (D) is $M n^{4 +}$
Electronic configuration of $M n^{4 +}$ = $[A r] 3 d^{3}$
Thus the number of unpaired electrons are 3.

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Similar questions

Q. (a) Pyrolusite on heating with

K O H

in the presence of air gives a dark green compound (A). The solution of (A) on treatment with

H_{2} {S O}_{4}

gives a purple coloured compound (B), which gives following reactions:
(i)

K I

on reaction with alkaline solution of (B) changes into a compound (C).
(ii) The colour of the compound (B) disappears on treatment with the acidic solution of

{F e S O}_{4}

.
(iii) With conc.

H_{2} {S O}_{4}

compound (B) gives (D) which can decompose to yield (E) and oxygen. Identify (A) to (E) and write balanced chemical equations for the formation of (A) and (B) and for the steps (i) to (iii).
(b) Complete and balance the following chemical equations.
(i)

A u + H C l + {H N O}_{3} ⟶ . . . . . . . . + . . . . . . . . + H_{2} O

(ii)

C + {H N O}_{3} (c o n c .) ⟶ {C O}_{2} + . . . . . . . . + H_{2} O

(iii)

S n + K O H (h o t) + H_{2} O ⟶ . . . . . . . + . . . . . . .

(iv)

{C u (O H)}_{2} + {N H}_{4} {N O}_{3} + {N H}_{4} O H ⟶ . . . . . + H_{2} O

Q. When

M n O_{2}

is fused with

K O H

in the presence of

K N O_{3}

as an oxidizing agent, it gives a dark green compound (A).
Compound (A) disproportionates in acidic solution to give purple compound (B).
An alkaline solution of compound (B) oxidises

K I

to compound (C) whereas an acidified solution of compound (B) oxidises

K I

to (D). Identify (A), (B), (C), and (D).

An organic compound A (molecular formula $C_{2} H_{4} O_{2})$ reacts with Na metal to form a compound B and evolves a gas which burns with a pop sound. Compound A on treatment with an alcohol C in the presence of a little of concentrated sulphuric acid forms a sweet-smelling compound D (molecular formula $C_{2} H_{6} O_{2})$ . Compound D on treatment with NaOH solution gives back B and C. Indentity A, B, C and D.