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Standard X
Chemistry
Precipitation Reaction
Compound A ...
Question

Compound A is a light-green crystalline solid. It gives the following tests :

(i) It dissolves in dilute sulphuric acid. No gas is produced.

(ii) A drop of KMnO4 is added to the above solution. The pink color disappears.

(iii) Compound A is heated strongly. Gases B and C, with a pungent smell, come out. A brown residue D is left behind.

(iv) The gas mixture (B and C) is passed into a dichromate solution. The solution turns green. But when only C is passed no change occurs.

(v) The green solution from step (iv) gives a white precipitate E with a solution of barium nitrate.

(vi) Residue D from step (iii) is heated on charcoal in a reducing flame. It gives a magnetic substance.

Thus, name the compound A is______ .

A
Fe(NO3)2
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B
Cr2(SO4)3
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C
FeSO4
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D
Fe2(SO4)3
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Solution

The correct option is C FeSO4
A light-green crystalline solid is expected to be ferrous sulphate.
There is no reaction with dilute sulphuric acid. With potassium permanganate, ferrous sulphate is oxidized to ferric sulphate and the pink colour disappears.
On strong heating, it gives two gases which are two oxides of sulphur, along with a brown residue, ferric oxide.
When gases are passed through acidified potassium dichromate, it is reduced by sulphur dioxide to give a green solution of chromium sulphate.
On adding barium sulphate, the green solution of sulphate gives a white precipitate of barium sulphate.
In charcoal cavity test, ferric oxide is reduced to iron which is magnetic.

FeSO4+dil⟶Noreaction

FeSO4+KMnO4H2SO4−−−−→Fe2(SO4)3+Mn2+(Pink)(Colorless)
FeSO4Δ−→Fe2O3+SO2↑+SO3↑
K2Cr2O7+SO2H2SO4−−−−→Cr2(SO4)3Green
H2O+SO3⟶H2SO4
H2SO4+Ba(NO3)2⟶2HNO3+BaSO4↓White

Therefore, C is correct option.

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Q. A hydrated metallic salt (A) , light green in colour gives a white anhydrous residue (B) after being heated gradually. (B) is soluble in water and its aqueous solution reacts with NO to give a dark brown compound (C). (B) on strong heating gives a brown residue (D) and a mixture of two gases (E) and (F). The gaseous mixture , when passed through acidified permanganate, discharged the pink colour and when passed through acidified BaCl2 solution, gives a white precipitate. Compounds (A), (B), (C) , (D) , (E) and (F) are identified as:
(A) : FeSO4.7H2O (B) : FeSO4,(C) : FeSO4.NO or [Fe(H2O)6NO]SO4], (D) : Fe2O3,(E) : SO2 and (F) : SO3
If true enter 1, else enter 0.
Q. An aqueous solution of salt (A), gives white crystalline precipitate (B) with NaCl solution. The filtrate gives a black precipitate (C) when H2S is passed through it. Compound (B) is dissolves in hot water and the solution gives a yellow precipitate (D) on treating with NaI and cooling. The compound (A) does not give any gas with dilute HCl but liberates reddish brown gas on heating.

Compound (A) is _________.

Q.
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 NH4OH and on passing H2S. 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:

Q.
Compound (A) is a greenish crystalline salt which gives the following results when tested :

(a) Addition of BaCl2 solution to a solution of (A) results in the formation of a white precipitate (B) which is insoluble in dilute HCl.
(b) On heating, water vapor and two gases (C) and (D) are liberated, leaving a red-brown residue (E).
(c) E dissolves in conc.HCl to give a yellow solution (F).
(d) With H2S, the solution (F) yields a yellow-white ppt. (G) which when filtrated, leaves a greenish filtrate (H).
(e) The solution (F) gives a green solution with SnCl2, and when reacted with K4[Fe(CN)6] gives a blue ppt.

Thus, gases (C) and (D) are :
Q. Two solid laboratory reagents (A) and (B) gives the following reactions:
Compound (A):
(i) on strongly heating gives two oxides of sulphur
(ii) on adding aqueous NaOH solution to its aqueous solution, a dirty green precipitate is obtained which starts turning brown on exposure to air
Compound (B) :
(iii) imparts green colour to the flame
(iv) Its solution does not give a precipitate on passing H2S
(v) When it is heated with solid K2Cr2O7 and concentrated H2SO4, a red gas is evolved. The gas when passed in an aq NaOH solution turns it yellow
Compound (A) and (B) are identified as FeSO4 and BaCl2.
If true enter 1, else enter 0.
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