Let the formula of sample be
(Fe2+)x (Fe3+)yO.
On looking at the given formula of the compound
x + y = 0.93 ... (1)
Total positive charge on ferrous and ferric ions should balance the two units of negative charge on oxygen. Therefore,
2x + 3y = 2 ... (2)
⇒ x + 3/2y = 1... (3)
On subtracting equation (1) from equation (3) we have
3/2y − y = 1 − 0. 93
⇒ 1/2y = 0.07
⇒ y = 0.14
On putting the value of y in equation (1) we get,
x + 0.14 = 0.93
⇒ x = 0.93 – 0.14
x = 0.79
Fraction of Fe2+ ions present in the sample = 0.79/0.93 = 0.81
Metal deficiency defect is present in the sample because iron is less in amount than that required for stoichiometric composition.
