﻿ Iron (II) oxide has a cubic structure and each of the unit cell is 5.0 A°. If density of the oxide is 4.0 g cm-3, calculate the number of Fe2+ and O2– ions present in each unit cell. from Chemistry The Solid State Class 12 Nagaland Board

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Iron (II) oxide has a cubic structure and each of the unit cell is 5.0 A°. If density of the oxide is 4.0 g cm-3, calculate the number of Fe2+ and O2– ions present in each unit cell.

Volume of the unit cell = (5 A°)
= (5 x 10–8 cm)3
= 125 x 10–24 cm3
= 1.25 x 10–22 cm3
Density of FeO = 4.0 g cm–3

Therefore, mass of the unit cell
= 1.25 x 10–22 cm3 x 4 g cm–3
= 5 x 10–22g
Mass of all molecules of FeO

Number of FeO molecules/unit cell

Thus, there are 4 Fe
2+ ions and 4O2– ions in each unit cell.

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