A sample of ferrous oxide has actual formula Fe0.93O1.00 . In this sample, what fraction of metal ions are Fe2+ ions? What type of non-stoichiometric defect is present in this sample?
Let the formula of the sample be (Fe2+)x.(Fe3+)y O
On looking at the given formula of the compound
x + y = 0.93 ...(i)
Total positive charge on ferrous and ferric ions should balance the two units of negative charge on oxygen Therefore,
2x + 3y = 2 ...(ii)
x + y = 1 ...(iii)
On subtracting equation(i) from equation (iii) we have
y - y = 1 - 0.93
y = 0.07
y = 0.14
On putting the value of y in equation (i), we get
x + 0.14 = 0.93 x = 0.93 - 0.14 x = 0.79
Fraction of Fe2+ ions present in the sample = = 0.849
Metal deficiency defect is present in the sample because iron is less in-amount than that required for stoichiometric composition.
