1. In a close-packed arrangement of identical spheres, each sphere touches how many nearest neighbours in three dimensions?
A.
4
B.
6
C.
8
D.
12
Correct Answer:
12
Explanation:
The coordination number of a sphere in a three-dimensional close-packed structure is 12, meaning it touches 12 nearest neighbours.
2. Which of the following represents the layer sequence in hexagonal close packing?
A.
ABCABC
B.
ABABAB
C.
AAAAAA
D.
AABBCC
Correct Answer:
ABABAB
Explanation:
Hexagonal close packing has an alternating ABAB layer sequence.
3. Which of the following represents the layer sequence in cubic close packing?
A.
ABAB
B.
AAAA
C.
ABCABC
D.
AABB
Correct Answer:
ABCABC
Explanation:
Cubic close packing has three different layers arranged in the repeating sequence ABCABC.
4. The packing efficiency of both hexagonal close packing and cubic close packing is approximately:
A.
52.4%
B.
68.0%
C.
74.0%
D.
84.6%
Correct Answer:
74.0%
Explanation:
Both hexagonal and cubic close-packed structures use about 74% of the available space.
5. In a close-packed arrangement, the number of octahedral voids is equal to the number of:
A.
Tetrahedral voids
B.
Close-packed particles
C.
Layers
D.
Cubic voids
Correct Answer:
Close-packed particles
Explanation:
For N particles in a close-packed structure, the number of octahedral voids is N.
6. If a close-packed structure contains N particles, how many tetrahedral voids are present?
A.
N/2
B.
N
C.
2N
D.
3N
Correct Answer:
2N
Explanation:
A close-packed arrangement containing N particles has 2N tetrahedral voids.
7. The coordination number of each particle in a two-dimensional close-packed layer is:
A.
4
B.
6
C.
8
D.
12
Correct Answer:
6
Explanation:
In a two-dimensional close-packed layer, each particle touches six neighbouring particles.
8. The second layer in a close-packed structure is placed in the:
A.
Cubic voids of the first layer
B.
Tetrahedral and octahedral voids equally
C.
Triangular voids of the first layer
D.
Centre of each sphere in the first layer
Correct Answer:
Triangular voids of the first layer
Explanation:
The spheres of the second layer occupy alternate triangular voids formed by the spheres in the first layer.
9. Which type of void is formed when a particle is surrounded by four particles in a close-packed structure?
A.
Octahedral void
B.
Tetrahedral void
C.
Cubic void
D.
Linear void
Correct Answer:
Tetrahedral void
Explanation:
A tetrahedral void is surrounded by four particles arranged at the corners of a tetrahedron.
10. Which type of void is formed when a particle is surrounded by six particles in a close-packed structure?
A.
Tetrahedral void
B.
Octahedral void
C.
Triangular void
D.
Linear void
Correct Answer:
Octahedral void
Explanation:
An octahedral void is surrounded by six particles, with three particles above and three below the void.
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