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 $
