CBSE Class 12 Chemistry 2020 Outside Delhi Set 1 Solved Paper

Question : 23 of 37

Marks: +1, -0

Write the balanced chemical equations involved in the preparation of

{\KMnO}_4

from pyrolusite ore

( {\MnO}_2)

.
OR
Write the balanced ionic equations showing the oxidising action of acidified dichromate

( {\Cr}_2 {\O}_7^{2-})

solution with
(i) Iron (II) ion and (ii) Tin (II) ion.

Solution:

2 {\MnO}_2+4 {\KOH}+ {\O}_2 → 2 {\K}_2 {\MnO}_4

+2 {\H}_2 {\O}

3 {\K}_2 {\MnO}_4+2 {\CO}_2 → 2 {\KMnO}_4+ {\MnO}_2↙{(\ppt)}

+2 {\K}_2 {\CO}_3

OR

(i)

{\Cr}_2 {\O}_7^{2-}+14 {\H}^{+}+6 {\Fe}^{2+} → 2 {\Cr}^{3+}

+6 {\Fe}^{3+}+7 {\H}_2 {\O}

(ii)

{\Cr}_2 {\O}_7^{2-}+3 {\Sn}^{2+}+14 {\H}^{+} → 2 {\Cr}^{3+}+3 {\Sn}^{4+}

+7 {\H}_2 {\O}

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