unit:6
class12 chemistry
1]Why do solids have a definite volume?
· The intermolecular forces of attraction that are present in solids are very strong.
· The constituent particles of solids have fixed position .
· Hence, solids have a definite volume.
2] classify the following as amorphous or crystalline solids.
|
Amorphous solids |
Crystalline solids |
|
Polyurethane |
Naphthalene |
|
Teflon |
Benzoic acid |
|
Cellophane |
Potassium nitrate |
|
Polyvinyl chloride |
Copper |
|
Fiber glass |
|
3]what type of stoichiometric defect is shown by ZnS
ZnS exhibits Frenkel defect.
4] ionic solids conduct electricity in molten state but not in solid state. Explain
In ionic compounds ,electricity is conducted by ions.
ü In solid state, ions are held together by strong electrostatic forces and not free to move about within the solid.
ü However in molten state or in solution form, the ions are free to move and can conduct electricity.
5]what type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?
- When a solid is heated vacancy defect can arise.
- A solid crystal is said to have vacancy defect when some of the lattice sites are vacant .
- Vacancy defect leads to a decrease in the density of the solid.
7] name an element with which silicon can be doped to give an n-type semi conductor.
Gallium
8] which point effect in crystal dosent alter the density of the relevant solids?
Frenkel defect.
9]Define the term amorphous.
A solid is said to be amorphous if its constituent particles are not arranged in a regular fashion.
Define void?
The empty spaces present between the atom or the ions when they are packed the crystal are called voids.
11]what is point defect in crystals?
The defects which are caused by missing misplaced atoms or ions in the crystal.
12] diamond and solid rhombic Sulphur covalent solids but the latter has very melting point than the former. Explain.
Diamond has network structure ,while sulphur does not .due to this particles of carbon are held at their positions firmly which makes diamond hard, brittle with extremely high melting point.
24]why is FeS not formed in stoichiometric composition?
In FeS,Fe2+ ions are replaced by Fe3+ ions. To maintain electrical neutrality,3 fe2+ ions are replaced by 2fe3+ ions .
21]Nacl has a sharp melting point but glass does not -justify
Nacl is a crystalline solid so possess sharp melting points where as glass is amorphous in nature so does not have sharp melting point.
19] what are primitive unit cells?
A unit cell contains only one lattice point is called a primitive unit cell, which made up from the lattice points at each of the corners
0 Comments