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The Solid State

Long Answer Type

151. An element occurs in BCC structure with cell edge of 300 pm. The density of the element is 5.2 g cm^–3. How many atoms of the element does 200 g of the element contain?

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Short Answer Type

152. 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).

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153. A metallic element exists as a cubic lattice. Each edge of the unit cell is 2.88 A°. The density of the metal is 7.20 g cm^–3. How many unit cells will be there in 100 g of the metal?

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154. The unit cell of an element of atomic mass 96, and density 10.3 g cm^–3 is a cube with edge length of 314 pm. Find the structure of crystal lattice (simple cubic, F.C.C. or B.C.C.) Avogadro’s constant. N_A = 6.023 x 10²³ mol^–1?

2325 Views

Long Answer Type

155. An element a crystallises in fcc structure. 200 g of this element has 4.12 x 10²⁴atoms. The density of A is 7.2 g cm^-3. Calculate the edge length of the unit cell?

solution:
we have given that
mass = 200g
density = 7.2 g cm^-3
N_A = 4.12 x 10²⁴
Z = 4
by using the following equation,

ρ = \frac{z \times M}{a^{3} \times N_{A}}

\Rightarrow

a^{3} = \frac{Z \times M}{d \times N}

= \frac{4 \times 200}{7.2 \times 4.12 \times 10^{24}} = \frac{800}{29.664} \times 10^{- 24}

a^{3} = 26.968 \times 10^{- 24} a = 2.997 \times 10^{- 8} a = 299.7 pm .

hence the edge length is 299.7pm

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Short Answer Type

156. An element crystallises in BCC structure. The edge length of its unit cell is 288 pm. If the density of crystal is 7.2 g cm^–3, what is the atomic mass of the element?

1664 Views

Long Answer Type

157. Caesium chloride crystallises as a body centred cubic lattice and has a density of 4.0 g cm^–3. Calculate the length of the edge of the unit cell of caesium chloride crystal.
[Molar Mass of CsCl = 168.5 g mol^–1, N_A = 6.02 x 10²³ mol^–1]

564 Views

Short Answer Type

158. The density of chromium is 7.2 g cm^–3. If the unit cell is cubic with edge length of 289 pm, determine the type of the unit cell (Atomic mass of Cr = 52 amu).

1682 Views

Long Answer Type

159. 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 O^2– ions present in each unit cell.

341 Views