D-And F-Block Elements Ques 4

Question: Acidified potassium dichromate is treated with hydrogen sulphide. In the reaction, the oxidation number of chromium

[MP PET 1996]

Options:

A) Increases from + 3 to + 6

B) Decreases from +6 to +3

C) Remains unchanged

D) Decreases from +6 to +2

Show Answer

Answer:

Correct Answer: B

Solution:

Decreases from + 6 to + 3.

$ K_2Cr_2O_7+4H_2SO_4,\to K_2SO_4+Cr_2{{(SO_4)}_3}+4H_2O+3O $

$ [H_2S+[O],\to ,S+H_2O]\times 3 $

$ \overset{+6}{\mathop{K_2Cr_2O_7}},+4H_2SO_4+3H_2S,\to $ $ K_2SO_4+\overset{+3}{\mathop{Cr}},{{(SO_4)}_3}+7H_2O+3S $



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