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When H2O2 is added to ice cold solution ...

When `H_2O_2` is added to ice cold solution of acidified potassium dichromate in ether and the contents are shaken and allowed to stand

A

A blue colour is obtained in ether due to formation of `Cr_2(SO_4)_3`

B

A blue colour is obtained in ether due to formation `CrO_5`

C

A blue colour is obtained in ether due to formation of `CrO_3`

D

Chromyl chloride is formed

Text Solution

Verified by Experts

The correct Answer is:
B
A blue colour is obtained in ether due to formation of `CrO_5`
`Cr_2 O_7^(-2) + 2H^(+) + 4H_2O_2 to 2CrO_5 + 5H_2O`
blue colour in ether
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K_2Cr_2O_7 acts as a good oxidizing agent in acidic medium underset("Orange")(Cr_(2)O_(7)^(2-)) + 14H^(+) + 6e^(-) rarr underset("Green")(2Cr^(3+)) + 7H_2O In alkaline solution, orange colour of Cr_(2)O_(7)^(2-) chages to yellow colour due to formation of Cr_2O_(4)^(2-) and again yellow colour changes to orange colour on changing the solution to acidic medium underset("Orange")(Cr_2O_7^(2-))+2OH^(_) rarrunderset("Yellow")(Cr_2O_7^(2-))+H_2O underset("Yellow")(2CrO_(4)^(2_-)) + 2H^(+) rarr underset("Orange")(Cr_(2)O_(7)^(2-) + H_(2)O) Cr_(4)^(2-) and Cr_(2)O_(7)^(2-) exist in equilibrium at pH =4 and are interconvertible by altering the pH of the solution. When heated with H_2SO_4 and metal chloride K_2Cr_2O_7 gives vapour of chromyl chloride (CrO_2Cl_2) . Chromyl chloride (CrO_2Cl_2) when passed into aqueous NaOH solution, yellow colour solution of CrO_(4)^(2-) is obtained. This on reaction with lead acetate gives yellow ppt. PbCrO_4 . When H_2O_2 is added to an acidified solution of dichromate ion, a complicated reaction occurs. The products obtained depend on the pH and concentration of dichromate. Cr_2O_7^(2-)+2H^(+) + 4H_(2)O_(2) rarr 2Cr(O_2)+5H_2O A deep blue-violet coloured peroxo compound, CrO(O_2)_2, ' called chromic peroxide is formed. This decomposes rapidly in aqueous solution into Cr^(3+) and xygen. Which of the following statements is wrong when a mixture of NaCI and K_2Cr_2O_2 is gently walmed with conc. H_2SO_4 ?

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