Engineering Questions with Answers - Multiple Choice Questions
MCQs on Manufacturing Engineering – Crystallography-1
1 - Question
Which of the following has a non-crystalline structure?
a) Iron
b) Quartz
c) Silica glass
d) Tungsten
View Answer
Answer: c
Explanation: In general, metals exist in a crystalline form. Iron and Tungsten being metals takes up body centered cubic crystalline structure at room temperature. The ceramic compound–silica (SiO2), can exist either in a crystalline form or in a non-crystalline form (amorphous form). While quartz, tridymite and cristobalite are known as its crystalline forms which are being differentiated based on SiO4 tetrahedra linkage style, silica’s non-crystalline (amorphous) form is just called as the silica glass.
2 - Question
Which of the following has less crystallinity?
a) Iron
b) Nickel
c) High density polythene
d) Low density polythene
View Answer
Answer: d
Explanation: It is clear that, iron and nickel being metals possesses a crystalline form, whereas high density polyethylene (HDPE) and low-density ethylene (LDPE) are a class of polymers. These both thermoplastics are semi-crystalline nature, out of which LDPE exhibits a crystallinity of about 50-60% and HDPE of about 90%. Some people may term HDPE as crystalline, but it is more appropriate to restrict it in the category of semi-crystalline class.
3 - Question
Which of the following is a characteristic of crystalline structure?
a) High density
b) Low density
c) Range of melting point
d) Short range of order
View Answer
Answer: a
Explanation: A crystalline structure has very close packing of atoms thus giving rise to high density to material it possesses when compared to its non-crystalline form. For example, quartz being the crystalline form of silica has a density of about 2.65 gm/cm3, whereas its ally–non-crystalline form silica glass has a density of 2.20 gm/cm3. For reference, the other properties being differentiated between crystalline and non-crystalline forms are tabulated below.
4 - Question
Which of the following is characteristic of non-crystalline structures?
a) Long range of periodicity
b) Well defined structure and geometry
c) Low density
d) Sharp diffraction pattern
View Answer
Answer: c
Explanation: In non-crystalline structure, there is no definite packing of atoms, which makes them to possess any random shape, further these atoms are being bonded by weak secondary bonds with Van der Wall’s forces, thus giving a low density to material.
5 - Question
Which of the following factor is not responsible for the formation of a non-crystalline structure?
a) Atomic packing has open structure
b) Primary bonds are absent
c) Formation of 1-dimensional chain molecule
d) Strong secondary bond
View Answer
Answer: d
Explanation: A non-crystalline structure is being formed by a secondary bonds or molecular bonds are formed as a result of weak Van der Wall’s of attractions which exist between various atoms. These intermolecular bonds can be further classified as dispersion bonds, dipole bonds, hydrogen bonds, which are all should be considered as weak secondary bonds.
6 - Question
Which of the following axis system is being satisfied by cubic crystal system?
a) a = b = c, α = β = γ = 90o
b) a ≠ b = c, α = β = γ = 90o
c) a = b ≠ c, α = β = γ = 90o
d) a = b = c, α ≠ β = ϒ = 90
View Answer
Answer: a
Explanation: Simple cubic have all sides equal and all angles equal. For reference, table of 7 Bravais lattices are tabulated below:
| S.No. | Crystal System | Conventional Unit Cell Axis System | |||||
|---|---|---|---|---|---|---|---|
| Lengths | Angles | ||||||
| 1 | Cubic | a = b = c | α = β = γ = 90o | ||||
| 2 | Tetragonal | a = b ≠ c | α = β = γ = 90o | ||||
| 3 | Orthorhombic | a ≠ b ≠ c | α = β = γ = 90o | ||||
| 4 | Rhombohedral (Trigonal) | a = b = c | α = β = γ ≠ 90o | ||||
| 5 | Hexagonal | a = b ≠ c | α = β = 90o, γ = 120o | ||||
| 6 | Monoclinic | a ≠ b ≠ c | α = γ = 90o ≠ β | 7 | Triclinic | a ≠ b ≠ c | α ≠ β ≠ γ ≠ 90o |
7 - Question
Which of the following axis system is being satisfied by tetragonal crystal system?
a) a = b = c, α = β = ϒ = 90o
b) a ≠ b ≠ c, α = β = ϒ = 90o
c) a = b ≠ c, α = β = ϒ = 90o
d) a = b = c, α ≠ β = ϒ = 90o
View Answer
Answer: c
Explanation: Tetragon has two sides equal and all angles equal.
8 - Question
Which of the following axis system is being satisfied by orthorhombic crystal system?
a) a = b = c, α = β = γ = 90o
b) a ≠ b ≠ c, α = β = γ = 90o
c) a = b ≠ c, α = β = γ = 90o
d) a = b = c, α ≠ β = γ = 90o
View Answer
Answer: b
Explanation: Orthorhombic have all sides unequal and all angles equal to a degree.
9 - Question
Which of the following axis system is being satisfied by rhombohedral (trigonal) crystal system?
a) a = b = c, α = β = γ = 90o
b) a ≠ b = c, α = β = γ = 90o
c) a = b ≠ c, α = β = γ = 90o
d) a = b = c, α = β = γ ≠ 90o
View Answer
Answer: d
Explanation: Rhombohedra have all sides equal and all angles equal but not 90o.
10 - Question
. Which of the following axis system is being satisfied by hexagonal crystal system?
a) a = b ≠ c, α = β = 90o, ϒ = 120o
b) a ≠ b = c, α = β = ϒ = 90o
c) a = b ≠ c, α = β = ϒ = 90o
d) a = b = c, α ≠ β = ϒ = 90o
View Answer
Answer: a
Explanation: Hexagonal have two sides equal and two angles equal to 90o and one angle equal to 120o.
11 - Question
Which of the following axis system is being satisfied by monoclinic crystal system?
a) a = b = c, α = β = 90o ≠ ϒ
b) a ≠ b = c, α = β = ϒ = 90o
c) a ≠ b ≠ c, α = β = 90o ≠ ϒ
d) a = b = c, α ≠ β = ϒ = 90o
View Answer
Answer: c
Explanation: Monoclinic have all sides unequal and two angles equal to 90o.
12 - Question
Which of the following axis system is being satisfied by triclinic crystal system?
a) a = b = c, α = β = ϒ = 90o
b) a ≠ b = c, α = β = ϒ = 90o
c) a ≠ b ≠ c, α ≠ β ≠ ϒ ≠ 90o
d) a = b = c, α ≠ β = ϒ = 90o
View Answer
Answer: c
Explanation: Triclinic structures have all sides unequal and all angles are also unequal.
13 - Question
Which one of the following is most symmetrical?
a) Simple cubic cell
b) Hexagonal
c) Triclinic
d) Tetragonal
View Answer
Answer: a
Explanation: In triclinic crystal system, we observe all the sides and angle to equal to each other (a = b = c and α = β = γ = 90o), thus giving highest symmetry (four 3-fold symmetry) among all 7 Bravais Lattices.
14 - Question
Which one of the following is least symmetrical?
a) Tetragonal
b) Simple cubic
c) Triclinic
d) Monoclinic
View Answer
Answer: c
Explanation: In triclinic crystal system, we observe all the sides and angle to unequal to each other (a ≠ b ≠ c and α ≠ β ≠ γ ≠ 90o), thus giving least symmetry (1-fold symmetry) among all 7 Bravais Lattices.
15 - Question
What is the coordination number of a simple cubic (SC) unit cell?
a) 4
b) 6
c) 8
d) 2
View Answer
Answer: b
Explanation: There are six nearest neighbouring atoms for every atom in a simple cubic (SC) unit cell, in other words, every atom in a SC unit cell is surrounded by 6 other atoms, thus coordination number of SC unit cell is is 6.
16 - Question
What is the coordination number of a face centered cubic (FCC) unit cell?
a) 4
b) 6
c) 8
d) 12
View Answer
Answer: d
Explanation: In an FCC structure, there are eight atoms, one atom each at the corner of the unit cell and one atom at the centre of each face. For any corner atom of the unit cell, the nearest atoms are face-centred atoms. Thus, the coordination number for an FCC structure = 4 centre atoms below the horizonal plane + 4 centre atoms above the horizontal plane + 4 centre atoms on the horizonal plane.
Hence, the coordination number for an FCC structure is 4 + 4 + 4 = 12.
17 - Question
What is the coordination number of body centered cubic unit cell?
a) 4
b) 6
c) 8
d) 2
View Answer
Answer: c
Explanation: For any corner atom of the BCC unit cell, the nearest atoms are the body centred atoms. There are eight-unit cells in neighbours with body-centered atoms. Hence, the coordination number for a BCC cubic unit cell is 8.
18 - Question
Effective number of atoms in a simple cubic (SC) unit cell is equal to _________
a) 4
b) 1
c) 8
d) 2
View Answer
Answer: b
Explanation: Total number of atoms at corners = 8 and each corner atom is shared by total 8-unit cells. Thus, effective number of atoms in an SC unit cell: 8 × 8⁄8 = 1.
19 - Question
Effective number of atoms in a face centered cubic (FCC) unit cell is equal to ________
a) 4
b) 1
c) 8
d) 2
View Answer
Answer: a
Explanation: In an FCC unit cell, there are eight atoms: one at each corner of the cube and six face centered atoms of the six planes of the cube. As corner atoms are shared by eight adjacent cubes and the face centered atoms by two adjacent unit cells, total effective number of atoms in an FCC unit cell will be 4.
20 - Question
Effective number of atoms in a body centered cubic (BCC) unit cell is equal to _____________
a) 4
b) 6
c) 1
d) 2
View Answer
Answer: d
Explanation: The unit cell of a cube contains eight atoms at the corners, which are shared by the eight adjoining cubes and one atom at the centre of the cube.
8 atoms at the corner: (8×1⁄8) = 1 atom + 1 centre atom in the unit cell, So, there are “2” effective number of atoms in a BCC unit cell.
21 - Question
The atomic packing fraction in a simple cubic unit cell is ________
a) 0.74
b) 0.52
c) 0.68
d) 0.66
View Answer
Answer: b
Explanation: a=r and APF = (volume of effective number of atoms/volume of unit cell).
22 - Question
The atomic packing fraction in a body centered cubic unit is cell is ________
a) 0.74
b) 0.52
c) 0.68
d) 0.66
View Answer
Answer: c
Explanation: r=(√3)/4×a and APF = (volume of effective number of atoms/volume of unit cell).
23 - Question
If the radius of a copper atom is given as 1.27 Ao, its density (in kg/m3) will be?
a) 100.01
b) 86.25
c) 8979
d) 7968
View Answer
Answer: c
Explanation: Formula to calculate the density of a cubic metal:
ρ (kg/m3) = n×A.Wa3 × 1.66 × 10-27
[where, ρ = density of metal, n = effective number of atoms per unit cell, A.W = Atomic weight of the metal in amu and a = lattice parameter in meter] Given: radius of copper = 1.27 Ao = 1.27×10-10 m
We know that atomic weight of copper = 63.5 amu
Lattice parameter to atomic radius relation for cubic structures are as follows:
| Crystal Structure | Effective Number of Atoms per Unit Cell | Effective Number of Atoms per Unit Cell |
|---|---|---|
| Simple Cubic (SC) | a = 2r | 1 |
| Body Centered Cubic (BCC) | a = 4r/√3 | 2 |
| Face Centered Cubic (FCC) | a = 4r/√2 | 4 |
| Hexagonal Close Packed Cubic (HCP) | a = 2r | 6 |
We know that copper has FCC crystal structure, so it has ‘4’ effective number of atoms per unit cell and given its atomic radius = 1.27×10-10 m
Therefore, lattice parameter of copper (a) = (4×1.27×10-10)/√2 = 3.59×10-10 m
Therefore, density of copper = 4×63.5(3.59×10−10)3 × 1.66 × 10-27 ≈ 8979 kg/m3.
24 - Question
The atomic packing fraction in a face centered cubic unit is?
a) 0.74
b) 0.52
c) 0.68
d) 0.66
View Answer
Answer: a
Explanation: a=2√2×r and APF = (volume of effective number of atoms/volume of unit cell).