CBSE Class 12 Chemistry 2016 Delhi Set 1 Solved Paper

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Question : 7
Total: 26
When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow coloured compound
(A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound
(B) on reaction with KCl forms a orange coloured crystalline compound (C).
(i) Write the formulae of the compounds (A), (B) and (C).
(ii) Write one use of compound (C).
OR
Complete the following chemical equations:
(i) MnO4+3S2O32+H2O ?
(ii) Cr2O72+3Sn2++14H+ ?
Solution:  
(i) 4FeCr2O4+16NaOH+7O2 8Na2CrO4[A]+2Fe2O3+8H2O
Na2Cr2O7[B]+2KClK2Cr2O7[C]+2NaCl
A:Na2CrO4B:Na2Cr2O7C:K2Cr2O7
(ii) Use of K2Cr2O7(C) : It is used as a strong oxidizing agent in industries.
OR
(i) 8MnO4+3S2O32+H2O8MnO2 +6SO42+2OH
(ii) Cr2O72+3Sn2++14H+2Cr3+ +7H2O+3Sn4+
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