25.0 mL of 0.05 M solution of NH2OH was boiled with excess of Fe3+ in acidic medium. The Fe2+ formed required 25.0 mL of 0.1 N Cr2O2−7 in acidic medium. What is oxidation number of the N in new product?
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Solution
1 equivalent of Fe3+ will react with 1 equivalent of K2Cr2O7. The number of milliequivalents of K2Cr2O7=0.1N×25.0mL=2.5meq.
This corresponds to the number of milliequivalents of Fe3+.
The number of moles of NH2OH is 0.05N×25.0mL=1.25meq. Thus, 2 moles of Fe3+ will combine with 1 mole of NH2OH.
Thus, the change in the oxidation number will be 2 i.e, from -1 to +1. 4Fe3+(aq)+2NH2OH(aq)→4Fe2+(aq)+N2O(g)+H2O(l)+4H+(aq)