KULLIYYAH OF ENGINEERING
MID SEMESTER EXAMINATION
SEMESTER II, 2019/2020 SESSION
Programme
: Materials Engineering
Level of Study
: UG 2
Time
: 10.00 am - 2.00 pm
Date
: 27/06/2020
Duration
: 4 Hrs
Course Code
: MATR 2381/MME 2503
Section(s)
: 1, 2, 3, 4, 5, 6
Course Title
: Materials Science and Engineering
This Question Paper Consists of 7 (Seven) Printed Pages (Including Cover Page)
With 5 (Five) Questions.
INSTRUCTION(S) TO CANDIDATES
DO NOT OPEN UNTIL YOU ARE ASKED TO DO SO
Answer All 5 (Five) Questions.
Only KoE approved calculator with approved sticker is allowed (non-programmable
and non-graphical).
Marks assigned to each problem are listed in the margins.
Total Marks for this paper is 80.
Weightage: 20%
Submit the answer sheet in PDF/JPEG form.
Any form of cheating or attempt to cheat is a serious offence which may
lead to dismissal.
Gadgets such as Mobile phones and Google glasses are prohibited in the
exam hall.
MATR 2381
QUESTION 1 (15 marks)
a) Briefly describe one of the following application in relation to the material
selection design and process for functionality of the product/device to be used
by consumer.
(6)
Sport Equipment
Automobile bodies
Fuel cells
b) Technological advancement and innovation has caused a massive transition of
computer design and functionality. Explain the causes of these changes as
shown in Fig.Q1(b) and relate it with material usage.
(4)
Fig.Q1(b)
c)
Single-Use Plastic Campaign on 14
February 2019 to protect and sustainability of the campus environment. Suggest
a solution with specific example how an engineer can contribute in addressing
this kind of issue from the engineering perspective.
(5)
QUESTION 2 (15 marks)
a)
Determine each of the configurations given below is an inert gas, a halogen, an
alkali metal, an alkaline earth metal or a transition metal. Justify your choices.
i.
ii.
iii.
iv.
v.
(5)
1s22s22p63s23p63d74s
1s22s22p63s23p6
1s22s22p5
1s22s22p63s2
1s22s22p63s23p64s1
b) Explain why hydrogen fluoride (HF) has a higher boiling temperature than
hydrogen chloride (HCl) (19.4 vs -85°C), even though HF has a lower
molecular weight.
Question Q2 continues in the next page
2
(3)
MATR 2381
c) Cesium bromide (CsBr) exhibits predominantly ionic bonding. The Cs+ and Brions have electron structures that are identical to which two inert gases?
Describe the ionic bonding between Cesium and Bromine.
d) Briefly described with illustrations the following types of primary bonding:
(i) ionic
(ii) covalent
(3)
(2)
(2)
QUESTION 3 (15 marks)
a)
The unit cell of an imaginary material is shown in Fig. Q3(a) (x, y and z axis
are perpendicular to each other).
(i) Which crystal system does this structure belong to?
(ii) Define the position of the atom in the middle of the unit cell.
(1)
(1)
Fig. Q3(a): A unit cell
b) Determine the indices for the directions in a cubic unit cell as shown in Fig.
Q3(b).
Fig. Q3 (b)
Question Q3 continues in the next page
3
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MATR 2381
c) Determine the Miller indices for the planes in a unit cell as shown in Fig.Q3(c).
(4)
Fig. Q3(c)
d) Within a cubic unit cell, sketch the following:
(i)
(ii)
(2.5)
(2.5)
QUESTION 4 (20 marks)
a) Using your own words, explain why crystalline solids are grouped into four
types: metallic solids, covalent network solids, ionic solids and molecular
solids.
b) Calculate the radius of an iridium atom (Ir), given that Ir has an FCC crystal
structure, a density of 22.4 g/cm3, and an atomic weight of 192.2 g/mol.
Question Q4 continues in the next page
4
(3)
(5)
MATR 2381
c)
(i) The edge length of the unit cell of LiCl (NaCl-like structure, FCC) is 0.514
nm or 5.14 Å. Assuming that the lithium ion is small enough so that the chloride
ions are in contact, as in Fig. Q4(b). Calculate the ionic radius for the chloride
ion.
(6)
Fig. Q4(b): Unit cell cubic structure
Note: The length unit angstrom, Å, is often used to represent atomic-scale
dimensions and is equivalent to 10 m.
(ii) Pure iron goes through a polymorphic change from BCC to FCC upon
heating at 912°C. Calculate the volume change associated with the change in
crystal structure from BCC to FCC if at 912°C the BCC unit cell has a lattice
constant a = 0.293 nm and the FCC unit cell a = 0.363 nm.
(6)
QUESTION 5 (15 marks)
a)
The simplest of the point defects is a vacancy, or vacant lattice site, one
normally occupied from which an atom is missing. From Fig. Q5(a), discuss
both vacancy and self-interstitial in solid crystalline.
(5)
Fig.Q5(a): Two-dimensional representations of a vacancy and a selfinterstitial
b)
Calculate the equilibrium number of vacancies per cubic meter for copper at
1250°C. The energy for vacancy formation is 1.5 eV/atom; the atomic weight
and density (at 1250°C) for copper are 65.2 g/mol and 9.1 g/cm3, respectively;
-5
eV/atom·K
Question Q5 continues in the next page
5
(6)
MATR 2381
c)
Impurity point defects are found in solid solutions, of which there are two types:
substitutional and interstitial. For the substitutional type, solute or impurity
atoms replace or substitute for the host atoms (Fig.Q5(c)). Identify several
features of the solute and solvent atoms that determine the degree to which the
former dissolves in the latter.
Fig.Q5 (c): Representations of substitutional and interstitial impurity
atoms
END OF PAPER
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(4)
MATR 2381
APPENDIX
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