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When KMnO4 is added to oxalic acid, the ...

When `KMnO_4` is added to oxalic acid, the decolourisation is slow in the begining but becomes instantaneous after sometime because

A

`Mn^(2+)` acts as autocatalyst

B

`CO_2` is fomed as the products

C

Reaction is exothermic

D

`MnO_(4)^(-)` catalyses the reaction

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The correct Answer is:
A
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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. What happens when a solution of potassium chromate is treated with an excess of dilute nitric acid?

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 ?

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. CrO_3 on reaction with HCl and the product on reaction with NaOH(aq) give respectively

When an acid solution of oxalic acid at 80^(@)C is titrated with KMnO_(4) solution, the first few drops of KMnO_(4) are decoloured slowly but decolourisation occurs fast later. This is because

AAKASH SERIES-D-BLOCK ELEMENTS-OBJECTIVE EXERCISE-2 (PRMANGANATE AND DICHROMATE)
  1. Acedified K2Cr2O7 cannot oxidise

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  2. Number of electrons transferred in each case when KMnO(4) acts as an o...

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  3. KMnO(4) is powerful oxidant where it converts into

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  4. Four moles of KMnO(4) reacts with excess of hypo solution to produce -...

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  5. An acidified solution of KMnO(4) oxidises

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  6. Incorrect statement regarding the structure of dichromate is

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  7. Reaction of KMnO4 in neutral or very weakly acidic solution can be rep...

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  8. K2Cr2O7 cannot be used for

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  9. A solution of potassium chromate is treated with an excess of dilute n...

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  10. The natures of the oxides CrO and CrO3, respectively

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  11. When acidified solution of potassium dichromate is shaken with aqueous...

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  12. In the dichromate dianion

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  13. The equilibrium Cr2O7^(2-) hArr 2CrO4^(2-)

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  14. Which of the following oxides of chromium is amphoteric in nature

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  15. Potassium permanganate acts as an oxidant in neutral, alkaline as well...

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  16. When KMnO4 is added to oxalic acid, the decolourisation is slow in the...

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  17. Acidified KMnO4 oxidizes nitrites to

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  18. Permanganate ion oxidize S2O3^(2-) in fairly alkaline solutions to giv...

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  19. When MnO(2) is fused with KOH in the presence of air, a coloured compo...

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