Solid State MCQ Questions & Answers in Physical Chemistry | Chemistry
Learn Solid State MCQ questions & answers in Physical Chemistry are available for students perparing for IIT-JEE, NEET, Engineering and Medical Enternace exam.
41.
A mineral having the formula $$A{B_2}$$ crystallizes in $$ccp$$ lattice with $$A$$ atoms occupying the lattice points. Pick out the correct statement of the following
A
100% occupancy of tetrahedral voids, $$C.N$$ of $$B = 4$$
B
100% occupancy of octahedral voids, $$C.N$$ of $$B = 4$$
C
50% occupancy of tetrahedral voids, $$C.N$$ of $$A = 4$$
D
100% occupancy of octahedral voids, $$C.N$$ of $$A = 4$$
Answer :
100% occupancy of tetrahedral voids, $$C.N$$ of $$B = 4$$
Number of $$A$$ cations per unit cell = 4
Number of $$B$$ anions per unit cell must be = 2 × 4 = 8
Number of tetrahedral voids per unit cell = 2 × 4 = 8
Number of octahedral voids per unit all = 1 × 4 = 4.
Hence, occupancy of tetrahedral voids = 100%
42.
Doping of silicon $$(Si)$$ with boron $$(B)$$ leads to :
A
$$n$$-type semiconductor
B
$$p$$-type semiconductor
C
Metal
D
Insulator
Answer :
$$p$$-type semiconductor
In a $$p$$ - type semiconductor, trivalent impurity from the III group elements is added as the impurity. trivalent impurities like Aluminium, Indium and Gallium are added to the intrinsic semiconductor. The Trivalent impurities added provides extra holes known as the acceptor atom. The majority carries in a $$p$$ - type semiconductor are holes.
In an $$n$$ - type semiconductor, pentavalent impurity from the V group is added to the pure semiconductor . Examples of pentavalent impurities are Arsenic, Antimony, Bismuth etc. The pentavalent impurities provide extra electrons and are termed as donor atoms. Electrons are the majority charge carries in $$n$$ - type semiconductors.
43.
Which of the following statements is true about semiconductors ?
A
Impurity of lower group creates $$n$$ - type semiconductors.
B
Impurity of higher group creates $$p$$ - type semiconductors.
C
Extrinsic semiconductors are formed by doping impurity.
D
Intrinsic semiconductors become conductors when temperature is raised.
Answer :
Intrinsic semiconductors become conductors when temperature is raised.
Intrinsic semiconductors are insulators at room temperature and become semiconductors when temperature is raised.
44.
Which type of ‘defect’ has the presence of cations in the interstitial sites?
A
Schottky defect
B
Vacancy defect
C
Frenkel defect
D
Metal deficiency defect
Answer :
Frenkel defect
In Frenkel defect some of ion ( usually cation due to their small size ) missing from their normal position and occupies position in interstitial position.
45.
A crystalline structure has radius ratio $$\left( {\frac{{{r_ + }}}{{{r_ - }}}} \right)$$ in the range of 0.225 - 0.414. The coordination number and arrangement of anions around the cations are
A
3, plane triangular
B
6, octahedral
C
4, tetrahedral
D
8, cubic
Answer :
4, tetrahedral
The radius ratio range of crystalline structure is 0.225 - 0.414. This range indicates 4 coordination number and tetrahedral arrangement.
46.
Which of the following statements is not correct about hexagonal close packing ?
A
In $$hcp,$$ atoms occupy 74 % the available space.
B
It is $$AB\,AB$$ type packing in which third layer is aligned with the first layer.
C
$$Be,Mg, Mo$$ etc. are found to have $$hcp$$ structure.
D
The coordination number is 6.
Answer :
The coordination number is 6.
The coordination number is 12.
47.
The lattice site in a pure crystal cannot be occupied by _________.
A
molecule
B
ion
C
electron
D
atom
Answer :
electron
Lattice sites in a pure crystal are occupied by the constituent units like atoms, molecules, ions but not occupied by electrons.
48.
The total number of tetrahedral voids in the face centred unit cell is __________.
A
6
B
8
C
10
D
12
Answer :
8
No. of atoms per unit cell in face centred unit cell = 4
∴ No. of tetrahedral voids = 2 × 4 = 8
49.
A solid with high electrical and thermal conductivity is
A
$$Si$$
B
$$Li$$
C
$$NaCl$$
D
$$Ice$$
Answer :
$$Li$$
Out of the given substances, only $$Li$$ has high electrical and thermal conductivity as $$Li$$ is a metallic solid.
50.
A compound is formed by two elements $$Y$$ and $$Z.$$ The element $$Z$$ forms $$ccp$$ and atoms $$Y$$ occupy $$\frac{1}{3}rd$$ of tetrahedral voids. The formula of the compound is
A
$${Y_2}{Z_3}$$
B
$$YZ$$
C
$$Y{Z_3}$$
D
$${Y_2}Z$$
Answer :
$${Y_2}{Z_3}$$
Suppose no. of atoms of $$Z = a$$
No. of tetrahedral voids $$ = 2a$$
No. of atoms of $$Y = \frac{1}{3} \times 2a = \frac{{2a}}{3}$$
Ratio of atoms of $$Y$$ and $$Z = \frac{{2a}}{3}:a = 2:3$$
Hence, the formula of the compound $$ = {Y_2}{Z_3}$$