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Properties of Acids

A white amorp...

Question

A white amorphous powder (A) when heated gives a colourless gas (B), which turns lime water milky and the residue (C) which is yellow when hot but white when cold. The residue (C) dissolves in dilute HCl and the resulting solution gives a white precipitate on addition of potassium ferrocyanide solution. (A) dissolves in dilute HCl with the evolution of a gas which is identical in all respects with (B). The solution of (A) as obtained above gives a white precipitate (D) on addition of excess of $N H_{4} O H$ and on passing $H_{2} S$ . Another portion of this solution gives initially a white precipitate (E) on addition of NaOH which dissolves in excess of it. Compounds (A) to (D) are identified as:

True

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False

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Solution

The correct option is B False
Zinc carbonate (A) is the white amorphous solid which on heating gives colourless gas (B) carbon dioxide and the residue (C) zinc oxide.
$Z n C O_{3} Δ - \to C O_{2} B + Z n O C$
Carbon dioxide gas turns lime water milky and zinc oxide is yellow when hot and white when cold.
Zinc oxide dissolves in dilute HCl to form zinc chloride which reacts with potassium ferrocyanide to form white ppt.
Zinc carbonate dissolves in dil HCl to liberate carbon dioxide gas (B).
$Z n C O_{3} + 2 H C l \to Z n C l_{2} + H_{2} O + C O_{2} ↑$
Ammonium hydroxide neutralizes excess HCl.
Zn(II) ions react with hydrogen sulphide to give a white ppt D ZnS.
$Z n^{2 +} + S^{2 -} \to Z n S ↑$
Zn(II) ions react with NaOH to form white precipitate E zinc hydroxide.
$Z n^{2 +} + 2 N a O H \to Z n (O H)_{2} w h i t e p p t, E$
This ppt dissolves in excess NaOH
$Z n (O H)_{2} w h i t e p p t, E + 2 N a O H \to N a_{2} Z n O_{2} s o d i u m z i n c a t e + 2 H_{2} O$

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Similar questions

Q. A white amorphous powder

A

on heating yields a colorless, noncombustible gas

B

and a solid

C

. The latter compound assumes a yellow color on heating and changes to white on cooling.

C

dissolves in dilute hydrochloric acid and the resulting solution gives a white precipitate with

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

solution. Dissolves in dilute

H C l

with the evolution of gas, which is identical in all respect with

B

. The gas

B

turns lime water milky, but the milkiness disappears with the continuous passage of gas. The solution of

A

as obtained above gives a white precipitate

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on the addition of an excess of

N H_{4} O H

and passing

H_{2} S

. Another portion of the solution gives initially a white precipitate

E

on the addition of

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solution, which dissolves on further addition of the base.

Identify the compound B.

Q. A white powder

A

on heating gave a non-combustible gas and a white residue. The residue on heating turns yellow. The residue dissolves in dilute

H C l

and the solution gives a white precipitate with

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

. Compound

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Q. A solution when diluted with

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and boiled, it gives a white precipitate. On addition of excess

N H_{4} C l

N H_{4} O H

the volume of precipitate decreases leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in

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N H_{4} C l

Q. A solution when diluted with

H_{2} O

and boiled, gives a white precipitate. On the addition of excess

N H_{4} C l / N H_{4} O H

, the volume of the precipitate decreases leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in

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Q. Read the following statements:
(i) A white amorphous powder (A) on strongly heating gives a colourless non-combustile gas (B) and solid (C).
(ii) The gas (B) turns lime water milky and turbidity disappear with the passage of excess of gas.
(iii) The solution (C) in dilute HCl gives a white precipitate with an aqueous solution of

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

.
(iv) The solution of (A) gives a white precipitate (D) on pasiing

H_{2} S

in presence of excess of

N H_{4} O H

.
Compound (A) to (D) are identified as:
(A) :

Z n C O_{3}

(B) :

C O_{2}

, and (C) :

Z n O

, and (D) :

Z n S

If true enter 1, else enter 0.

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