A sample of ferrous oxide has actual formula Fe_0.93O_1.00. In this sample what fraction of metal ions are Fe²⁺ ions? What type of nonstoichiometric defect is present in this sample?

For 1→ O there is 0.93 Fe

Let 100→ O^2- is present in sample. To maintain neutrality Fe²⁺ and Fe³⁺ should be present in such a ratio that it counterbalances the negative charge.

Let number of Fe²⁺ be X

number of Fe³⁺ be 93-X

since total positive charge must be equal to total negative charge as compound is overall neutral,

2X+3(93-X)=2× 100

2X+279-3X=200

X=79

Fe²⁺ =79

Fe³⁺ =93-79=14

Fraction of Fe²⁺ is = 0.849.

This is metal deficiency defect as iron present in sample is in less amount than required for stoichiometric composition.