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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
Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2 :1. Can you account for the fact that this substance is a p-type semi-conductor ?

In the sample of cuprous oxide, Cu2O prepared in laboratory, copper to oxygen ratio is less than 2 : 1 and this deficiency of copper causes the metal deficiency defects.
In these defects the positive ions are less in number as compared to anions. These defects are caused in two ways:
(i) By Cation Vacancies : Some Cu+ may be missing from lattice sites and their positive charges are balanced by presence of extra charge on adjacent cations i.e., some Cu2+ are present and some cation vacancies are present.

(ii) By presence of extra anions at interstitial sites: The type of defect can arise where some oxide ion, O2– are present at lattice sites and their charge is balanced by neighbouring cations in higher oxidation states i.e., some Cu2+ ions are present instead of Cu2+ ions.

Metal deficiency defect due cation vacancy.

Metal deficiency defect due to presence of extra anions.


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 .

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.

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.

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.