Food Processing Unit Operations Multiple Choice Questions on “Crystal Geometry”.
1. How are crystals classified?
a) According to the place of origin
b) According to the position of the unit cells
c) According to the symmetry of the unit cells
d) According to the purity of the unit cells
Answer: c
Clarification: The crystals structures are classified according to the symmetry of the unit cells. There are in 7 groups, collectively called Crystal Systems, they are monoclinic, tricinic, orthorhombic, tetragonal, trigonal, cubic and hexagonal.
2. Are these statements about the Lattice points true?
Statement 1: It is a point in a crystal with specific arrangement of atoms.
Statement 2: A primitive unit cell contains more than one lattice point.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: Lattice point is a point in a crystal with specific arrangement of atoms, replicated many times in the crystal. A primitive unit cell contains one lattice point.
3. What is crystallography?
a) Description of arrangement of atoms
b) Description of the purity of crystals
c) Description of the sign language
d) Description of the crystals history
Answer: a
Clarification: The crystal structure is given in the form of description of the ordered arrangement of atoms, ions or molecules in a crystalline material is called as crystallography.
4. What is crystal basis?
a) Disposition of the atoms around each lattice point
b) Description of the purity of crystals
c) Description of arrangement of atoms
d) Description of the crystals history
Answer: a
Clarification: The actual nature of the atoms or ions around each lattice point is called the crystal basis. From the provisional details of the bonding and the crystal chemistry, it can contain more than one stoichiometric unit.
5. What is the most common crystal structure?
a) Face-centered cubic and square packed structures
b) Face-centered cubic and hexagonal close-packed structures
c) Square packed structures and hexagonal close-packed structures
d) Square packed structures and parallelogram packed structure
Answer: a
Clarification: A Face-centered cubic (FCC) unit cell contains atoms at all the corners of the crystal lattice and also at the center of all the faces of the cube whereas hexagonal close-packed (hcp) arrangement has a unit cell which consists of three layers of atoms. The top and bottom layers contain six atoms at the corners of a hexagon and one atom at the center of each hexagon.
6. Is Diamond A Crystal?
a) True
b) False
Answer: a
Clarification: Diamond is a crystal form of carbon. The particular crystal structure is face-centered cubic and often called as diamond cubic crystal structure.
7. What is the strongest crystal structure?
a) Diamond
b) Cubic boron nitride
c) Silicon carbide
d) Graphite
Answer: a
Clarification: Diamond is the hardest material and cubic boron nitride is the second-hardest. Silicon carbide is very structurally complex and has at least 70 crystalline forms.
8. Who discovered crystal structure?
a) Max von Laue
b) Erasmus Jacobs
c) Nicholas-Jacques Conte
d) A.L. Lavoisier
Answer: a
Clarification: Max von Laue discovered the crystal structure. Erasmus Jacobs discovered diamonds. Nicholas-Jacques Conte invented graphite and A.L. Lavoisier discovered carbon.
9. What are Miller indices?
a) Set of three numbers used to indicate the position of a face of a crystal
b) Set of four numbers used to indicate the position of a face of a crystal
c) Set of five numbers used to indicate the position of a face of a crystal
d) Set of six numbers used to indicate the position of a face of a crystal
Answer: a
Clarification: Miller indices are a set of three numbers to indicate the position of a face of a crystal and are determined on the basis of the reciprocal of the intercept of the face on the crystallographic axes.
10. Is honeycomb lattice a Bravais lattice?
a) True
b) False
Answer: b
Clarification: The honeycomb lattice is not a Bravais lattice. The Bravais lattice of a honeycomb lattice is a hexagonal lattice. For a Bravais lattice, all lattice sites are equal.