JEE Main On 16 April 2018 Question 7

Question: When $ XO _2 $ is fused with an alkali metal hydroxide in presence of an oxidizing agent such as $ KNO _3; $ a dark green product is formed which disproportionaltes= in acidic solution to afford a dark purple solution X is: [JEE Main 16-4-2018]

Options:

A) Cr

B) V

C) Ti

D) Mn

Show Answer

Answer:

Correct Answer: D

Solution:

$ \underset{(green)}{\mathop{MnO _2+2KOH+KNO _3\to K _2MnO _4+KNO _2+H _2O}}, $

Disproportionation reaction is as following:

$ \underset{(purple)}{\mathop{MnO_4^{-}2+4{H^{+}}\to 2MnO_4^{-}+MnO _2+2H _2O}}, $