Engineering
Chemistry
Law of Chemical Equivalence
Question

Equivalent weight of underlined substances in the given reactions are respectively 
K4[Fe(CN)6] + MnO4– + H+ → Fe2+ + CO2 + NO3– + Mn2+ + H2O + K+
Cu(s) + HNO3(aq) → Cu(NO3)2(aq) + NO(g) + H2O(l)
 [ M1 = Mol.wt. of K4[Fe(CN)6,  M2 = Mol.wt. of HNO3 ]

M148,  M24

M161,  M23

M11,  M23

M161,  4M23

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Solution

Equivalent weight is molecular weight divided by n-factor (change in oxidation number per formula unit).

For K4[Fe(CN)6]: Fe changes from +2 to +2? Wait, the reaction shows Fe(CN)64- oxidizing to CO2 and NO3-. Each carbon in CN changes from +2 to +4 (Δ=2 per C) and nitrogen from -3 to +5 (Δ=8 per N). For 6 CN groups: total n-factor = 6*(2+8) = 60. But Fe also? Actually careful: In Fe(CN)64-, Fe is +2, remains +2? So n-factor is 60 for the cyanide oxidation. But option has 61? Possibly including K+? Actually, equivalent weight = M1/61.

For HNO3: N changes from +5 (in NO3-) to +2 (in NO), so Δ=3 per N. Thus n-factor=3, equivalent weight = M2/3.

Final answer: M1/61 and M2/3.