Solid State Quiz-4
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Q1. The appearance of colour in solid alkali metal halide is generally due to:
Solution
Presence of excess Na in NaCl and there by causing anion vacancy defect makes it yellow, presence of excess Li in LiCl makes it pink and presence of excess K in KCl makes it violet. Greater the number of F-centres, greater is intensity of colour.
Presence of excess Na in NaCl and there by causing anion vacancy defect makes it yellow, presence of excess Li in LiCl makes it pink and presence of excess K in KCl makes it violet. Greater the number of F-centres, greater is intensity of colour.
Q2.Sodium metal crystallizes in a body centred cubic lattice with the cell edge a=4.29 Å . The radius of sodium atom is :
Solution
Radius of Na(if bcc lattice) =√3/4 a
Radius of Na(if bcc lattice) =√3/4 a
=√3/4 x 4.29
= 1.8574 Å
Q3. Schottky defect is noticed in :
Solution
All these show Schottky defect.
All these show Schottky defect.
Q4. Which is the wrong statement regarding a crystal containing Schottky defect?
Solution
When equal number of cations and anions are missing from their position in a crystal lattice so that electrical neutrality is maintained, the defect is called Schottky defect. Due to missing of ions, the overall density of the crystal decreases. Moreover, defect leads to randomness, thus entropy also increases.
When equal number of cations and anions are missing from their position in a crystal lattice so that electrical neutrality is maintained, the defect is called Schottky defect. Due to missing of ions, the overall density of the crystal decreases. Moreover, defect leads to randomness, thus entropy also increases.
Q5.The mass of a unit cell of CsCl corresponds to :
Solution
An unit cell of CsCl having bcc structure consists of 8 atoms at the corner and one atom at centre. Thus, no. of
=8 ×1/8=1
and no. of 
=1×1=1
Thus, no. of CsCl unit per unit cell = 1
An unit cell of CsCl having bcc structure consists of 8 atoms at the corner and one atom at centre. Thus, no. of
=8 ×1/8=1
and no. of 
=1×1=1
Thus, no. of CsCl unit per unit cell = 1
Q6. If the distance between 
ions in sodium chloride crystal is X pm, the length of
ions in sodium chloride crystal is X pm, the length of the edge of the unit cell is
Solution
In NaCl, the length of the edge of the unit cell is=2× distance between ions hence,
In NaCl, the length of the edge of the unit cell is=2× distance between
ions hence, a=2X pm.
Q7.
possesses :
possesses :
Solution
has fcc structure with 8 : 4 co-ordination and has 4 units of CaF2 per unit cell.
has fcc structure with 8 : 4 co-ordination and has 4 units of CaF2 per unit cell.
Q8. Which arrangement of electron decides ferrimagnetism?
Solution
Ferrimagnetism involves magnetic dipoles oriented in parallel and antiparallel direction in unequal number to give some net dipole moment.
Ferrimagnetism involves magnetic dipoles oriented in parallel and antiparallel direction in unequal number to give some net dipole moment.
Q9.Extremely pure samples of Ge and Si are non-conductors, but their conductivity increases suddenly
on introducing ….in their crystal lattice.
Solution
Doping of elements of group 14 (Ge and Si) with group 15 (As) elements produces excess of electrons and shows n -type conduction, the symbol n indicating flow of negative charge in them. Doping of elements of group 14 (Ge and Si)with group 13 (B) elements products hole (electron deficiency) in the crystal and shows P-type conduction, the symbol p indicating flow of positive charge.
Doping of elements of group 14 (Ge and Si) with group 15 (As) elements produces excess of electrons and shows n -type conduction, the symbol n indicating flow of negative charge in them. Doping of elements of group 14 (Ge and Si)with group 13 (B) elements products hole (electron deficiency) in the crystal and shows P-type conduction, the symbol p indicating flow of positive charge.
Q10. The structure of CsCl crystal is
Solution
The co-ordination number of sc, fcc and bcc structure are 6,12 and 8 respectively. CsCl has body centred cubic structure having 8 : 8 co-ordination number.
The co-ordination number of sc, fcc and bcc structure are 6,12 and 8 respectively. CsCl has body centred cubic structure having 8 : 8 co-ordination number.
