A sample of iron(II) oxide has the formula Fe_0.94O with only Fe^2+ and Fe^3+ ions. Find the percentage of iron present as Fe^3+ (nearest integer).

JEE Advanced levelNumerical answerDifficulty 3 of 3ss105

A sample of iron(II) oxide has the formula $Fe X_{0.94} O$ with only $Fe X^{2 +}$ and $Fe X^{3 +}$ ions. Find the percentage of iron present as $Fe X^{3 +}$ (nearest integer).

Numerical answer type, answer in %, tolerance 0.5.

Let

Fe X^{3 +} = x

per O.

3 x + 2 (0.94 - x) = 2

gives

x = 0.12

. Fraction

= 0.12/0.94 = 0.1277

, so 12.77%

\approx 13%