JEE Main · 2005 · 08 May 2005 · Offline · Redox Reactions and Electrochemistry

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The oxidation state of chromium in the final product formed by the reaction between KI and acidified potassium dichromate solution is

(A)+4
(B)+6
(C)+2
(D)+3✓ Correct

Answer: (D)

Solution

In acidified potassium dichromate the chromium starts in its

+ 6

state as

Cr X_{2} O X_{7} X^{2 -}

. Potassium iodide is a reducing agent, and in the acidic medium it reduces the dichromate while itself being oxidised to iodine. The chromium is pulled down from

+ 6

to the green

Cr X^{3 +}

ion, so its oxidation state in the final product is

+ 3

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option

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