Iron (II) oxide has a cubic structure and each unit cell has side 5A. If the density of the oxide is 4 g cm^–3, calculate the number of Fe²⁺ and O^2– ions present in each unit cell. (Molar mass of FeO = 72 g mol^–1, N_A = 6.02 x 10²³ mol^–1).

Solution

Solution:
We have given
volume of the unit cell = (5 x 10^-8cm)³ = 1.25 x 10^-22cm³

Density of FeO = 4g cm^-3

Density,

$ρ = \frac{z \times M}{a^{3} \times N_{A}} 4 = \frac{z \times 72}{(5 \times 10^{- 8})^{3} \times 6.02 \times 10^{23}} z = \frac{4 \times 1.25 \times 10^{- 22} \times 6.02 \times 10^{23}}{72} = 4.18 ≅ 4$

Each unit cell has four units of FeO. So it has four Fe²⁺ and four O^2– ions.

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The Solid State

Iron (II) oxide has a cubic structure and each unit cell has side 5A. If the density of the oxide is 4 g cm^–3, calculate the number of Fe²⁺ and O^2– ions present in each unit cell. (Molar mass of FeO = 72 g mol^–1, N_A = 6.02 x 10²³ mol^–1).

Some More Questions From The Solid State Chapter

Why are solids rigid?

Why do solids have a definite volume?

Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Why is glass considred a super-cooled liquid?

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show clevage property?

Classify the following solids in different categories based on the nature of intermolecular forces operating in them:
Potassium sulphate, tin, benzene, urea, ammonia, water, zinc
sulphate, graphite, rubidium, argon, silicon carbide.

Solid A is a very hard, electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?

Ionic solids conduct electricity in liquid state but not in solid state. Explain.

What type of solids are electrical conductors, malleable and ductile?

Give the significance of a 'lattice point'.

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The Solid State

Iron (II) oxide has a cubic structure and each unit cell has side 5A. If the density of the oxide is 4 g cm–3, calculate the number of Fe2+ and O2– ions present in each unit cell. (Molar mass of FeO = 72 g mol–1, NA = 6.02 x 1023 mol–1).

Some More Questions From The Solid State Chapter

Why are solids rigid?

Why do solids have a definite volume?

Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Why is glass considred a super-cooled liquid?

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show clevage property?

Classify the following solids in different categories based on the nature of intermolecular forces operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphate, graphite, rubidium, argon, silicon carbide.

Solid A is a very hard, electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?

Ionic solids conduct electricity in liquid state but not in solid state. Explain.

What type of solids are electrical conductors, malleable and ductile?

Give the significance of a 'lattice point'.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Iron (II) oxide has a cubic structure and each unit cell has side 5A. If the density of the oxide is 4 g cm^–3, calculate the number of Fe²⁺ and O^2– ions present in each unit cell. (Molar mass of FeO = 72 g mol^–1, N_A = 6.02 x 10²³ mol^–1).

Classify the following solids in different categories based on the nature of intermolecular forces operating in them:
Potassium sulphate, tin, benzene, urea, ammonia, water, zinc
sulphate, graphite, rubidium, argon, silicon carbide.