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Oxides of Sulphur

A green color...

Question

A green colored water soluble substance, $(A)$ , forms a greenish precipitate $(B)$ with $N H_{4} O H$ in presence of $N H_{4} C l$ (excess). When $(B)$ is oxidized with a little sodium bismuthate in presence of $H_{2} S O_{4}$ , a orange solution is obtained. If now a little solid $N a_{2} O_{2}$ is added, an intensely blue-colored compound is formed, extractable with ether. $(A)$ yields a bulky white precipitate with $B a C l_{2}$ solution. Suggest the nature of the compound $(A)$ :

Nickel (II) sulphate

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Copper (II) sulphate

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Chromium (III) sulphate

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Ferrous sulphate

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Solution

The correct option is C Chromium (III) sulphate
Compound (A) is chromium (III) sulphate $C r_{2} (S O_{4})_{3}$ .
It is green coloured and water soluble. In presence of excess $N H_{4} C l$ , it reacts with $N H_{4} O H$ to form green precipitate of chromium (III) hydroxide $C r (O H)_{3}$
When chromium (III) hydroxide is oxidized with a little sodium bismuthate in presence of $H_{2} S O_{4}$ , a orange solution is obtained. If now a little solid $N a_{2} O_{2}$ is added, an intensely blue-colored compound is formed, extractable with ether.
Chromium (III) sulphate yields a bulky white precipitate of barium sulphate $B a S O_{4}$ with $B a C l_{2}$ solution.
$C r_{2} (S O_{4})_{3} + 3 B a C l_{2} \to 3 B a S O_{4} + 2 C r C l_{3}$

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Similar questions

A black colored compound (A) on reaction with dilute

H_{2} S O_{4}

gives a gas (B) which on passing in a solution of acid (C) gives white turbidity (D). Gas (B) when placed in an acidified solution of a compound (E) gives a precipitate (F) soluble in dilute

H N O_{3} .

After boiling this solution, when an excess of

N H_{4} O H

is added, blue colored compound (G) is formed. To this solution on addition of

C H_{3} C O O H

and aqueous

K_{4} [F e (C N)_{6}]

, a chocolate precipitate (H) is obtained. On the addition of an aqueous solution of

B a C l_{2}

to an aqueous solution of E, a white ppt insoluble in

H N O_{3}

is obtained.

Identify B.

A black colored compound (A) on reaction with

d i l . H_{2} S O_{4}

gives a gas (B) which on passing in a solution of acid (C) gives white turbidity (D). Gas (B) when passed in an acidified solution of a compound (E) gives a black precipitate (F) which is soluble in hot concentrated (C). After boiling this solution when an excess of ammonia solution is added, a blue-colored compound (G) is formed. To the solution of (E), on the addition of acetic acid and aqueous potassium ferrocyanide, a chocolate brown precipitate (H) is formed. On the addition of an aqueous solution of

B a C l_{2}

to an aqueous solution of (E), white precipitate insoluble in

H N O_{3}

is obtained.

The gas (B) on passing through an acid (C) gives white turbidity (D) because :

A black colored (insoluble in

H_{2} O

) solid A does not dissolve in

H N O_{3}

. Aqua regia can dissolve A forming B. B gives yellow precipitate C with

N a O H

. B also gives an orange ppt. D with

K I

. D dissolves in excess of

K I

forming E. E gives brown ppt. with

N H_{4}^{+}

salt in presence of

N a O H

. A is precipitated if

H_{2} S

gas is passed into the solution of B in

d i l . H C l

The compound C is :

Q. The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained along with potassium nitrate solution. Gas C does not burn itself but helps to burn other things.
What is compound B?

A colorless solid (A) when placed into water produces a heavy white turbidity to (B). Solid (A) gives a clear solution in

c o n c . H C l

when

H C l

solution is added to large amounts of water, (B) forms again. (B) dissolves in dilute HCl. When

H_{2} S

is passed through a suspension of (A) or (B); a black precipitate (C) forms, (C) is insoluble in yellow ammonium sulphide

(N H_{4})_{2} S

C o n c . H_{2} S O_{4}

added to solid (A) liberates gas (D). Gas(D) is water-soluble and gives white precipitate with mercuric salts (E) and not mercuric salts. The black precipitate (C) dissolves in

H N O_{3}

(1:1) to give a solution to which

H_{2} S O_{4}

is added followed by addition of

N H_{4} O H

when a white precipitate (F) is formed. (E) gives a black ppt. (G) with solution of sodium stannite.

When compound (A) reacts with

N H_{4} O H

, then product is a:

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