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Byju's Answer

Standard XII

Chemistry

Electrophilic Substitution Reactions of Haloarenes

a Pyrolusite ...

Question

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

(A) is

K_{2} {M n O}_{4}

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(B) is

{K M n O}_{4}

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(D) is

{M n}_{2} O_{7}

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(E) is

{M n O}_{2}

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all of these correct

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Solution

The correct option is E all of these correct
(a) The dark green compound (A) is $K_{2} {M n O}_{4}$
The purple coloured compound (B) is ${K M n O}_{4}$
The compound (C) is ${K I O}_{3}$
The compound (D) is ${M n}_{2} O_{7}$
The compound (E) is ${M n O}_{2}$
manganese dioxide reacts with potassium hydroxide solution to form potassium manganate.
${M n O}_{2} + 2 K O H + \frac{1}{2} O_{2} ⟶ K_{2} {M n O}_{4} + H_{2} O$
Potassium manganate on reaction with sulphuric acid gives potassium permanganate.
${3 M n O}_{4}^{2 -} + {4 H}^{+} ⟶ {2 M n O}_{4}^{-} + {M n O}_{2} + {2 H}_{2} O$
Following are the reactions given by potassium permananate.
(i) ${2 M n O}_{4}^{-} + I^{-} + H_{2} O Δ \to {I O}_{3}^{-} + {2 M n O}_{2} + {2 O H}^{-}$
(ii) ${M n O}_{4}^{-} + {8 H}^{+} + {5 F e}^{2 +} ⟶ {5 F e}^{3 +} + {M n}^{2 +} + {4 H}_{2} O$
(iii) ${2 M n O}_{4}^{-} + {2 H}^{+} ⟶ {M n}_{2} O_{7} + H_{2} O$
${2 M n}_{2} O_{7} Δ \to {4 M n O}_{2} + {3 O}_{2}$
(b) The balanced chemical reactions are as given below.
(i) $A u + 4 H C l + {H N O}_{3} ⟶ {H A u C l}_{4} + N O + {2 H}_{2} O$
(ii) $C + {H N O}_{3} ⟶ {C O}_{2} + {4 N O}_{2} + {2 H}_{2} O$
(iii) $S n + 2 K O H + H_{2} O ⟶ K_{2} {S n O}_{3} + {2 H}_{2}$
(iv) ${C u (O H)}_{2} + {2 N H}_{4} {N O}_{3} + {2 N H}_{4} O H ⟶ [{C u [({N H}_{3})}_{4}]_{4}] ({N O}_{3})_{2} + {4 H}_{2} O$

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Similar questions

Q. 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)?

Q. (i) A blue coloured compoud (A) on heating gives two products, (B) and (C).
(ii) A metal (D) is deposited on passing hydrogen through heated (B).
(iii) The solution of (B) in

H C l

on treatment with

gives a choclate brown coloured precipitated of compound (E).
(iv) (C) turns lime water milky which disappears on continous passage of (C) forming a compound (F).
Identify (A) to (F) and give chemical equations for the reactions at steps (i) to (iv).

Q. Write four characteristics of a neutral organic compound '

A

' is

C_{2} H_{6} O

which gives the following reactions:
(i) Gives an acidic compound '

B

' on oxidation with acidified potassium dichromate.
(ii) Compound '

A

' on heating with '

B

' in presence of concentrated

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

gives a sweet smelling substance '

C

'.
Identify the compounds

A, B, C

. Give the equation of the related reactions.

Q. (i) A black mineral (A) on heating in presence of air gives a gas (B).
(ii) The mineral (A) on reaction with dilute

H_{2} S O_{4}

gives a gas (C) and solution of a compound (D).
(iii) On passing gas (C) into an aqueous solution (B), a white turbidity is obtained.
(iv) The aqueous solution of compound (D) on reaction with potassium ferricyanide gives a blue compound (E).

Compounds (A) to (E) are identified as:

(A) :

F e S

, (B) :

S O_{2}

, (C) :

H_{2} S

, (D) :

F e S O_{4}

and (E) :

K F e^{I} I [F e^{I} I I (C N)_{6}]

If true enter 1, else enter 0.

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).

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