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JEE Main 20137 April
Exam
JEE Main
Year
2013
Date
7 April
Subject
Chemistry
Chapter
Some Basic Concepts of Chemistry

JEE Main 2013 · 7 April · Chemistry · Some Basic Concepts of Chemistry

Experimentally it was found that a metal oxide has formula M _ 0.98...

Experimentally it was found that a metal oxide has formula M0.98O{M}_{0.98}O. Metal M, is present as M2+{M}^{2 +} and M3+{M}^{3 +} in its oxide. Fraction of the metal which exists as M3+{M}^{3 +} would be:

Options

  1. A6 . 05\text{%}
  2. B5 . 08\text{%}
  3. C7 . 01\text{%}
  4. D4 . 08\text{%}

Correct answer

D. 4 . 08\text{%}

Step-by-step 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{M}^{3 +} = \dfrac{0 .04}{0 .98} \times 100 = 4 .08 %
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