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Potassium dichromate acts as a strong ox...

Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with `H_2O_2` due to the formation of (P)
The orange red fumes obtained on heating potassium dichromate with a metal chloride and conc. `H_2SO_4` is due to the formation of

A

`CrO_3`

B

`CrO_5`

C

`CrO_2Cl_2`

D

`CrOCl_2`

Text Solution

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The correct Answer is:
To solve the question step by step, we will analyze the reactions involving potassium dichromate and its interactions with other chemicals as described in the problem. ### Step 1: Understanding the Reaction Potassium dichromate (K2Cr2O7) acts as a strong oxidizing agent in acidic medium. When it is heated with a metal chloride (like NaCl) and concentrated sulfuric acid (H2SO4), it produces orange-red fumes. ### Step 2: Identifying the Product of the Reaction The orange-red fumes produced in this reaction are due to the formation of chromyl chloride (CrO2Cl2). The balanced equation for the reaction can be represented as: \[ K_2Cr_2O_7 + 6 H_2SO_4 + 4 NaCl \rightarrow 2 CrO_2Cl_2 + 2 KHSO_4 + 4 NaHSO_4 + 3 H_2O \] ### Step 3: Passing Fumes Through Sodium Hydroxide When these orange-red fumes (CrO2Cl2) are passed through sodium hydroxide (NaOH), a yellow solution (X) is formed. The reaction can be represented as: \[ CrO_2Cl_2 + 4 NaOH \rightarrow Na_2CrO_4 + 2 NaCl + 2 H_2O \] Here, sodium chromate (Na2CrO4) is the yellow solution (X). ### Step 4: Formation of Yellow Precipitate When the yellow solution (X) is acidified, it reacts with lead acetate (Pb(CH3COO)2) to form a yellow precipitate (Y), which is lead chromate (PbCrO4): \[ Na_2CrO_4 + Pb(CH_3COO)_2 \rightarrow PbCrO_4 \downarrow + 2 NaCH_3COO \] ### Step 5: Heating Potassium Dichromate with KOH When potassium dichromate is heated with potassium hydroxide (KOH), it forms a yellow solution (Z), which is also sodium chromate (K2CrO4): \[ K_2Cr_2O_7 + 2 KOH \rightarrow 2 K_2CrO_4 + H_2O \] This yellow solution (Z) changes to orange color upon acidification, reverting back to potassium dichromate (K2Cr2O7). ### Step 6: Reaction with Hydrogen Peroxide The acidified solution of dichromate ions (Cr2O7^2-) gives a deep blue color with hydrogen peroxide (H2O2) due to the formation of chromium (III) ions (Cr^3+): \[ Cr_2O_7^{2-} + H_2O_2 + 14 H^+ \rightarrow 2 Cr^{3+} + 7 H_2O \] The deep blue color is due to the formation of the complex ion with chromium. ### Conclusion The orange-red fumes obtained on heating potassium dichromate with a metal chloride and concentrated sulfuric acid are due to the formation of **chromyl chloride (CrO2Cl2)**. ---
To solve the question step by step, we will analyze the reactions involving potassium dichromate and its interactions with other chemicals as described in the problem. ### Step 1: Understanding the Reaction Potassium dichromate (K2Cr2O7) acts as a strong oxidizing agent in acidic medium. When it is heated with a metal chloride (like NaCl) and concentrated sulfuric acid (H2SO4), it produces orange-red fumes. ### Step 2: Identifying the Product of the Reaction The orange-red fumes produced in this reaction are due to the formation of chromyl chloride (CrO2Cl2). The balanced equation for the reaction can be represented as: \[ ...
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Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow solution (X) is

Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow solution (Z) on acidification gives

Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow precipitate (Y) corresponds to

Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The oxidation state of Cr in compound P

Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The blue colour of compound P fades due to the formation of

The cation which gives a yellow precipitate with potassium chromate is

Which of the following aqueous solution is colourless but gives yellow precipitate on adding lead acetate to it

The orange colour of dichromate solution changes of blue on heating with alkalies due to the formation of chromate ions.

Knowledge Check

  • Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow solution (X) is

    A
    `K_2CrO_4`
    B
    `Na_2CrO_4`
    C
    `CrCl_3`
    D
    `Cr(OH)_3`

  • Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow solution (Z) on acidification gives

    A
    `K_2CrO_4`
    B
    `K_2Cr_2O_7`
    C
    `K_2SO_4`
    D
    `(CH_3COO)_2Pb`

  • Potassium dichromate acts as a strong oxidising agent in the acidic medium. When heated with a metal chloride and conc. sulphuric acid, it gives orange red fumes. On passing these fumes through sodium hydroxide, it gives a yellow solution (X) and this acidified solution gives yellow precipitate (Y) with lead acetate. On heating potassium dichromate with KOH, it forms a yellow solution (Z) which on acidification changes to orange colour. Acidified solution of dichromate ion gives deep blue colour with H_2O_2 due to the formation of (P) The yellow precipitate (Y) corresponds to

    A
    `PbS`
    B
    `PbCO_3`
    C
    `PbCrO_4`
    D
    `PbSO_4`