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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
If NaCl is doped with 10–3 mol % of SrCl2' what is the concentration of cation vacancies?

We know that two Na+ ions are replaced by each of the Sr2+ ions while SrCl2 is doped with NaCl. But in this case, only one lattice point is occupied by each of the Sr2+ ions and produce one cation vacancy.

Here 10 – 3 mole of SrCl2 is doped with 100 moles of NaCl Thus, cation vacancies produced by NaCl = 10 – 3 mol Since, 100 moles of NaCl produces cation vacancies after doping = 10 –3 mol

Therefore, 1 mole of NaCl will produce cation vacancies after doping

10 to the power of negative 3 end exponent over 100 space equals 10 to the power of negative 5 end exponent space mol
therefore, total cationic vacancies
=10-5 x Avogadro's number
=10-5  x 6.023 x 1023
=6.023 x 10-18 vacancies


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 .

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 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.

Why do solids have a definite volume?

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