Q12 / 90 · JEE Main 2013 (07 Apr) · Chemistry

Experimentally it was found that a metal oxide has formula M0.98O. Metal M, is present as M2+ and M3+ in its oxide. Fraction of the metal which exists as M3+ would be:

  • A
    6.05%
  • B
    5.08%
  • C
    7.01%
  • Correct answer
    D
    4.08%

Solution

Consider one mole of the oxide, then

Moles of M = 0.98;     Moles of O2- = 1

Let 'x' moles of M are in +3 oxidation state, then Moles of M2+ = 0.98-x

On doing charge balancing we get 

(0.98 - x)2 + 3x  = 2

Or 1.96 - 2x + 3x - 2 = 0

Or x = 0.04

 ∴ %of M3+=0.040.98×100=4.08%

Hence, the correct answer is option: 'D'.

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