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प्रश्न
Answer the following question.
When MnO2 is fused with KOH in the presence of KNO3 as an oxidizing agent, it gives a dark green compound (A). Compound (A) disproportionates in an acidic solution to give a purple compound (B). An alkaline solution of compound (B) oxidizes KI to compound (C) whereas an acidified solution of compound (B) oxidizes KI to (D). Identify (A), (B), (C), and (D).
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उत्तर
Potassium permanganate is prepared by fusion of MnO2 with an alkali metal hydroxide and an oxidizing agent like KNO3. This produces the dark green K2MnO4 which disproportionates in a neutral or acidic solution to give permanganate.
\[\ce{2MnO2 + 4KOH + O2 -> \underset{\text{(A) Dark Green}}{2K2MnO4}+ 2H2O}\]
\[\ce{3MnO^2-_4 + 4H^+ ->\underset{\text{(B) purple}}{2MnO^-_4} + MnO2 + 2H2O}\]
In acid solutions:
Iodine is librated from potassium iodine:
\[\ce{10I^- +\underset{\text{(B)}}{2MnO^-_4}+ 16H^+ -> 2Mn^2+ + 8H2O +\underset{\text{(D)}}{5l2}}\]
In neutral or faintly alkaline solution:
A notable reaction is the oxidation of iodine to iodate:
\[\ce{\underset{\text{(B)}}{2MnO^-_4}+ H2O + I^- -> 2MnO2 + 2OH^- + \underset{\text{(C)}}{IO^-_3}}\].
संबंधित प्रश्न
Complete the following equation :
`2MnO_4^(-)+6H^++5NO_2^(-)rarr`
Give an example and suggest a reason for the following feature of the transition metal chemistry:
A transition metal exhibits the highest oxidation state in oxides and fluorides.
Give an example and suggest a reason for the following feature of the transition metal chemistry:
The highest oxidation state is exhibited in oxoanions of a metal.
Indicate the steps in the preparation of KMnO4 from pyrolusite ore.
On addition of small amount of \[\ce{KMnO4}\] to concentrated \[\ce{H2SO4}\], a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.
In the form of dichromate, \[\ce{Cr (VI)}\] is a strong oxidising agent in acidic medium but \[\ce{Mo (VI)}\] in \[\ce{MoO3}\] \[\ce{and W (VI)}\] in \[\ce{WO3}\] are not because:
(i) \[\ce{Cr(VI)}\] is more stable than \[\ce{Mo(VI)}\] and \[\ce{and W(VI)}\].
(ii) \[\ce{Mo(VI)}\] and \[\ce{and W(VI)}\] are more stable than \[\ce{Cr(VI)}\].
(iii) Higher oxidation states of heavier members of group-6 of transition series are more stable.
(iv) Lower oxidation states of heavier members of group-6 of transition series are more stable.
KMnO4 is coloured due to ______.
Complete the following ionic equation:
\[\ce{Cr2O^{2-}7 + 2OH^- ->}\]
Complete the reaction mentioning all the products formed:
\[\ce{Cr2O^{2-}7 + 3H2S + 8H^+ ->}\]
Indicate the steps in the preparation of \[\ce{K2Cr2O7}\] from chromite ore.
