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The Solid State

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Chemistry I

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Calculate the density of silver which crystallizes in a face centred cubic lattice with unit cell length 0.4086 nm (At. mass of Ag = 107.88)

We have given that

Unit cell length,
a = 0.40806 nm  = 4.086 x 10-10 m

  If fcc lattice the number of atoms per unit cell,
i.e. Z = 4

        M for Ag = 107.88 g mol-1

                      =1.0788×10-1 kg mol-1

              NA = 6.023 × 1023

Density of Ag, d = ZMNA a3

                         = 4×1.0788×10-16.023×1023×(4.086×10-10)3= 1.051 × 104 kg m-3

 Thus the density of silver is 1.051 x 104 kgm-3


Why are solids rigid?

Solids are rigid because the internuclear distance between the  molecules of a solid are very less and closely packed and their positions are fixed due to the strong forces of attraction between them.

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

Amorphous solids: Polyurethane, teflon, cellophane, polyvinyal chloride, fibre glass.
Crystalline solids: naphthlene, benzoic acid, potassium nitrate, copper.

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?

Refractive index of a solid which have the same value along all directions are isotropic in nature. It would not show cleavage property.

Why do solids have a definite volume?

A solid have a definite volume because the inter molecular distance  between its molecules are fixed.

Why is glass considred a super-cooled liquid?

Glass is amorphous solids and  have a tendency to flow, though very slowly. Therefore, these are called pseudo solids or super cooled liquids .