ALLOYS AND PHASE RULE
ALLOYS:
INTRODUCTION- DEFINITIONPROPERTIES OF ALLOYSSIGNIFICANCE OF ALLOYING, FUNCTIONS AND EFFECT OF ALLOYING ELEMENTS
- 1.What kind of steel requires definite
amounts of other alloying elements?
a) Carbon steel
b) Alloying steel
c) Stainless steel
d) Tool steel
Answer: b
Explanation: Alloy steels are those steels
which require a specific amount of the
elements making up its composition. Alloy
steels consist of manganese, silicon, and
copper as primary elements whose quantities
are equal to or more than 1.65%, 0.60%, and
0.60% respectively. - 2.Which of these is not a function of alloy
steels?
a) Increases strength
b) Improves ductility
c) Reduces cost
d) Improves machinability
Answer: c
Explanation: Alloy steels are used to
improve properties such as strength, hardness,
ductility, grain structure, and machinability,
among others. This, however, results in
increased costs due to multiple elements
involved in the process. - 3.Steels containing up to 3% to 4% of one or
more alloying elements are known as
a) Low alloy steels
b) HSLA steels
c) High alloy steels
d) Stainless steels
Answer: a
Explanation: Low alloy steels consist of 3%
to 4% of alloying elements making up its
composition. They have similar
microstructure and heat treatments as plain
carbon steels. HSLA and AISI steels are the
types of low alloy steels.
- 4.What does AISI steel stand for?
a) American-Indian Steel Institute
b) American-Indian Society of Iron
c) American Iron and Steel Institute
d) Alloys, Iron and Steel Institute
Answer: c
Explanation: American Iron and Steel
Institute (AISI) is an association, established
in America, which produces steel. AISI steels
are used in machine construction. They are
otherwise known as construction steels or
structural steels. - 5.Which of these is not an application of
HSLA steels?
a) Bridges
b) Automobiles and trains
c) Building columns
d) Leaf and coil springs
Answer: d
Explanation: HSLA steels are known as
high-strength-low-alloy steels. These high
strength steels are primarily used as structural
materials or construction alloys. They are
used to reduce weight on bridges,
automobiles, pressure vessels, building
columns, etc. - 6.Steels containing more than 5% of one or
more alloying elements are known as
a) HSLA steels
b) High alloy steels
c) Tool and die steels
d) Stainless steels
Answer: b
Explanation: High alloy steels are composed
of more than 5% of alloying elements. They
have different microstructure and heat
treatments than those of plain carbon steels.
Tool and die, and stainless steels are the types
of high alloy steels. - 7.Which of the following groups of alloying
elements stabilize austenite?
a) Ni, Mn, Cu, and Co
b) Cr, W, Mo, V, and Si
c) Cr, W, Ti, Mo, Nb, V, and Mn
d) Co, Al, and Ni
Answer: a
Explanation: The alloying elements such as
Ni, Mn, Cu, and Co have a tendency to
alleviate austenite, whereas Cr, W, Mo, V, and
Si tend to stabilize ferrites. Alloying elements
such as Cr, W, Ti, Mo, Nb, V, and Mn tend to
form carbides. Other elements like Co, Al,
and Ni help to weaken carbides and thereby
form graphite. - 8.Which family of steels are referred to as
chromoly?
a) 40xx
b) 41xx
c) 43xx
d) 44xx
Answer: b
Explanation: The family of 41xx steel is
usually called as chromoly or chrome-moly
due to its primary alloying elements,
chromium and molybdenum. Steels such as
4130 and 4140 are generally used for bicycle
frames, and as parts of firearms, flywheels
etc. - 9.What is the common name of COR-TEN
steel?
a) Weathering steel
b) Control-rolled steel
c) Pearlite-reduced steel
d) Microalloyed steel
Answer: a
Explanation: Weathering steels are otherwise
also known as COR-TEN or corten steels.
These steels produce a corrosion resistance,
which makes them ideal for eliminating the
need to paint. All choices¸ including corten
steels are classifications of HSLA steels.
- 10.Alloy steels containing 0.05% to 0.15% of
alloying elements are called
a) Weathering steel
b) Stainless steel
c) Tool and die steel
d) Microalloyed steel
Answer: d
Explanation: Microalloyed steels contain
alloying elements in small quantities (0.05%
to 0.15%). These elements include niobium,
vanadium, titanium, molybdenum, rare earth
metals, among others. They are used to refine
the microstructure of the grain or for
precipitate hardening process.
NICHROME AND STAINLESS STEEL (18/8)
- 1.Which is the primary element used for
making stainless steel alloy?
a) Chromium
b) Zirconium
c) Vanadium
d) Indium
Answer: a
Explanation: Stainless steels contain iron and
a minimum of 10.5% of chromium. This
gives it great resistance to corrosion.
Therefore, stainless steels are often known as
corrosion-resistant steels or chromiumbearing steels. - 2.Addition of gives stainless steels
an austenitic structure.
a) Molybdenum
b) Carbon
c) Nickel
d) Vanadium
Answer: c
Explanation: Nickel is added to stainless
steels with a 3.5% to 22% composition to
form austenitic structure. This results in the
highest corrosion resistance among all
stainless steels. They also possess high
strength and ductility. - 3.Stainless steels with little carbon and no
nickel are called
a) Ferritic stainless steel
b) Austenitic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Answer: a
Explanation: Ferritic stainless steels are
steels containing 12.5% to 17% of chromium.
They are nickel¬-free and contain very little
carbon making up its composition. They are,
therefore, better resistant to corrosion than
martensitic stainless steels. - 4.Stainless steels with high strength, but low
corrosion resistance are known as
a) Austenitic stainless steel
b) Ferritic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Answer: c
Explanation: Martensitic stainless steels are
made of 12-14% chromium, along with
molybdenum, nickel, and carbon. This makes
the steels hard and brittle, but poorly resistant
to corrosion. Martensitic stainless steels are
used in making Swiss army knives. - 5.Which of the following are applications of
Ferritic stainless steels?
a) Aircraft engine parts, heat exchangers
b) Milk, kettles
c) Oil burner parts, furnace elements
d) Pumps and valve parts
Answer: c
Explanation: Ferritic stainless steels have the
ability to be welded, forged, rolled, and
machined. They are used for making oil
burner parts and furnace elements. Austenitic
stainless steel is used to make engine parts,
milk cans; Pumps and valve parts are
applications of martensitic stainless steels.
- 6.Which of the following is not a type of oilhardening steel?
a) O1
b) O2
c) O6
d) O9
Answer: d
Explanation: Oil hardening steels are a group
of cold working tool steels. This group
consists of O1 (0.9% C, 1% Mn, 0.5% Cr),
O2 type (0.9% C, 1.5% Mn, 0.3% Si), O6
type (1.65% C, 1% Si, 0.25% Mo, and an O7
type. - 7.Mushet steel belongs to which group of
tool steels?
a) Oil-hardening steels
b) Air-hardening steels
c) High-speed steels
d) Hot-working steels
Answer: b
Explanation: Mushet steel was the first airhardening tool steel. It belongs to the Coldworking family of tool steels. It was developed by Robert Mushet. - 8.What property does the AISI-SAE tool
steel grade ‘L’ possess?
a) Cold-working
b) Hot-working
c) Plastic mild
d) Special Purpose
Answer: d
Explanation: The steel grade ‘L’ refers to
special purpose steel containing low alloy. It
consists of elements such as carbon,
chromium, manganese, and a few others. The
L2 and L6 are the most commonly used steels
under this category. - 9.low-carbon, high-alloyed steels which
possess high strength and toughness are
known as
a) Carbon steels
b) Alloy steels
c) Maraging steels
d) Stainless steels
Answer: c
Explanation: Maraging steels are those high
strength steels which have tensile strengths up
to 1900 MPa. They are composed of 18% Ni,
7% Co, and less than 0.05% C. - 10.What do TRIP steels stand for?
a) Transformation Induced Porosity
b) Transformation Induced Plasticity
c) Transformation Induced Pearlite
d) Transformation Induced Property
Answer: b
Explanation: TRIP steels are those steels
containing high strength and ductility. They
are mainly used for automotive industry
needs. The expanded form of TRIP is
Transformation Induced Plasticity. It contains
an austenite microstructure. - 11.What is the maximum allowable
temperature at which High-Speed Steels
retain good cutting ability?
a) 100oC
b) 200oC
c) 350oC
d) 540oC
Answer: d
Explanation: High-speed steels have the
ability to remove and cut metal at a much
higher rate than carbon steels. They have a
good cutting ability even at a temperature as
high as 540oC. Above this temperature, they
soften and lose their cutting edge.
- 12.Ultra high-speed steels are made of which
of the following elements?
a) Tungsten and molybdenum
b) Chromium and molybdenum
c) Vanadium and cobalt
d) Molybdenum and cobalt
Answer: c
Explanation: Ultra high-speed steels have
greater tool lives and greater cutting
efficiency. This is due to the addition of
vanadium (up to 4%) and cobalt (5% to 12%)
along with carbon, chromium, and tungsten. - 13.What is the microstructure of Hadfield’s
steel?
a) Austenite
b) Ferrite
c) Martensite
d) Cementite
Answer: a
Explanation: Hadfield’s manganese steels
(Mangalloy) possess great strength and
toughness. Its austenite structure is obtained
by heating it. This also results in high wear
resistance, which finds its applications in
bulldozers, crushers, etc.
HEAT TREATMENT OF STEEL.
- 1.Which of the following is the hardest
constituent of steel?
a) Ledeburite
b) Austenite
c) Bainite
d) Martensite
Answer: d
Explanation: Martensite is the hardest
constituent of steel. The primary reasons
accounting for this could be, the internal
strains within BCC iron due to the excess
carbon presence and due to the plastic
deformation of parent FCC iron (austenite)
surrounding the martensitic plate. Rate of
cooling and the amount of carbon percentage
in steel are directly proportional to the
amount of hardness achieved in martensitic
transformation. - 2.Iron possesses BCC crystal structure up to
(in degree centigrade)?
a) 1539
b) 768
c) 910
d) 1410
Answer: b
Explanation: Pure iron possess either BCC or
FCC crystal structure as its temperature is
increased from room temperature to its
melting point. At room temperature to 910oC,
it is having BCC, between 910oC and 1410oC
it is having face centered cubic, and from
1410oC to its melting point (1539oC) it
returns to its BCC crystal structure. - 3.Iron possesses BCC crystal structure above
(in degree centigrade)?
a) 1539
b) 768
c) 910
d) 1410
Answer: d
Explanation: From 1410oC to its melting
point (1539oC) iron is having BCC crystal
structure. - 4.Iron possesses FCC crystal structure above
(in degree centigrade)?
a) 1539
b) 768
c) 910
d) 1410
Answer: c
Explanation: Between 910oC and 1410oC
iron is having face centered cubic crystal
structure.
- 5.Which of the following form of iron is
magnetic in nature?
a) α
b) δ
c) γ
d) λ
Answer: a
Explanation: The alpha form of iron is
magnetic and stable at all temperatures below
910oC. - 6.For steel, which one of the following
properties can be enhanced upon annealing?
a) Hardness
b) Toughness
c) Ductility
d) Resilience
Answer: c
Explanation: A furnace cooling technique,
annealing will enhance the ductility of steel,
due to the formation of coarse pearlite. - 7.In Annealing, cooling is done in which of
the following medium?
a) Air
b) Water
c) Oil
d) Furnace
Answer: d
Explanation: In annealing, after
solutionising, material is used to furnace cool,
means furnace is switched off and the steel
sample inside is let cool down. - 8.In normalizing, cooling is done in which of
the following medium?
a) Air
b) Water
c) Oil
d) Furnace
Answer: a
Explanation: In normalizing, steel is heat
treated above its critical temperature,
solutionised, and then allowed to cool for a
long time by keeping it in air. In steel, it
forms fine pearlite, which imparts strength to
steel. - 9.Mild steel can be converted into high
carbons steel by which of the following heat
treatment process?
a) Annealing
b) Normalizing
c) Case hardening
d) Nitriding
Answer: c
Explanation: Case hardening, also referred as
carburizing increases carbon content of steel,
thus, imparting hardness to steel. - 10.Upon annealing, eutectoid steel converts
to which of the following?
a) Perlite
b) Cementite
c) Austenite
d) Martensite
Answer: a
Explanation: Eutectoid steels upon annealing
produces pearlite (coarse pearlite). Pearlite is
an alternate lamellae of ferrite and cementite.
PHASE RULE:
INTRODUCTION, DEFINITION OF TERMS WITH EXAMPLES, ONE COMPONENT SYSTEM.
- 1.What is Gibbs phase rule for general
system?
a) P = C – 1 – F
b) P = C + 1 – F
c) P + F = C – 2
d) P + F = C + 2
Answer: d
Explanation: The number of degrees of
freedom, F (no. of independently variable
factors), number of components, C, and
number of phases in equilibrium, P.
- 2.What is Gibbs phase rule for metallurgical
system?
a) F = C – 1 – P
b) F = C + 1 – P
c) P + F = C – 2
d) P + F = C + 2
Answer: b
Explanation: For metallurgical system
pressure has no appreciable effect on phase
equilibrium and hence, F = C – P + 1. - 3.In a single – component condensed system,
if degree of freedom is zero, maximum
number of phases that can co – exist
a) 2
b) 3
c) 0
d) 1
Answer: a
Explanation: Given F = 0
Then p = c + 1, c = 1
.: P = 2.
4.4.The degree of freedom at a triple point in the unary diagram for water is
a) 2
b) 3
c) 0
d) 1
Answer: c
Explanation: For three phase system degree
of freedom is 0.
- 5.What is degree of freedom for single –
phase fields on the phase diagram?
a) 2
b) 3
c) 0
d) 1
Answer: a
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
.:F = 2.
- 6.What is degree of freedom when two
phases co – exist?
a) 2
b) 3
c) 0
d) 1
Answer: d
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
F = 3 – 2 = 1.
7.What is degree of freedom when three
phases co – exist?
a) 2
b) 3
c) 0
d) 1
Answer: c
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
F = 3 – 3 = 0.
- 8.For single component system when degree
of freedom is 1(one) then number of phases
a) 2
b) 3
c) 0
d) 1
Answer: d
Explanation: F = C + 1 – P
F = 2 – P (C = 1)
→ p = 2 – F = 2 – 1 = 1.
- 9.When α, L and β phase fields touch the
isotherm line what are the respective phase
compositions?
a) 8.0 wt%, 71.9 wt%, 91.2 wt% of Ag
b) 8.0 wt%, 91.2 wt%, 71.9 wt% of Ag
c) 71.9 wt%, 91.2 wt%, 8.0 wt% of Ag
d) 91.2 wt%, 8.0 wt%, 71.9 wt% of Ag
Answer: a
Explanation: For binary systems, when three
phases are present, there will be F = 0, so
composition is fixed.
- 10.For binary alloy consisting of three phases
of non – equilibrium one, What will be the
temperature of these phases?
a) Different
b) Constant
c) Same
d) Two of them will be with one temperature
Answer: c
Explanation: One use of the Gibbs phase rule
is in analyzing for non – equilibrium
conditions by analyzing with above method
we come to know (under these
Circumstances, three phases will exist only at
a single temperature).
REDUCED PHASE RULE
- 1.What does Gibb’s phase rule state?
a) P+F=C-1
b) P+F=C+1
c) P+F=C-2
d) P+F=C+2
Answer: d
Explanation: The above phase rule is a
formula that gives the condition for finding
the number of phases in a system. This phase
rule can be applied to both condensed as well
as normal systems. - 2.What is the point at which all the three
phases of a system exist?
a) Triple point
b) Sublimation point
c) Vapor point
d) Eutectic point
Answer: a
Explanation: Since at the triple point, the
degree of freedom is zero (that is invariant
reaction takes place at that point), therefore
according to phase rule, F=C-P+2.
Substituting the known values, we get P=3
(all states). - 3.For water system, the number of phases at
the triple point is
a) 0
b) 1
c) 2
d) 3
Answer: d
Explanation: Since at the triple point, the
degree of freedom is zero, while applying the
formula F=C-P+2, we get the number of
phases as three because C=1, F=0 (since
water system forms only single component).
- 4.Liquid phase exists for all compositions
above region.
a) Eutectic region
b) Equilibrium region
c) Isometric region
d) Sublimation region
Answer: c
Explanation: In a phase region above the
eutectic point, both the solid and liquid
phases exist together where the region is bi
variant and this region is called isometric
region. Here the region has 2 degrees of
freedom. - 5.Select the wrong statements from the
following statements with respect to a phase
diagram.
a) Gives information about concentration
b) Gives information about solubility
c) Gives information on melting and boiling
points
d) Gives information on relative
concentration
Answer: d
Explanation: A phase diagram gives
information only on the concentration of
species, their solubility rate, degree of
freedom and other physical properties. It does
not explain about transformation rates and
relative concentration (relative
concentration=total concentration/equilibrium
concentration). - 6.Select a non-homogeneous system from the
following.
a) Salt solution
b) Sugar solution
c) Glucose in water
d) Saturated solution of NaCl
Answer: d
Explanation: A homogeneous mixture is one
which is miscible completely with one
another. In any saturated solution, when the
amount of solute reaches more than a critical
point, then the solution becomes
heterogeneous. - 7.Select the odd statement with respect to a
phase reaction.
a) Saturated solution
b) Equilibrium solution
c) Concentric solution
d) Amorphous solution
Answer: a
Explanation: A terminal solution, an
intermediate solution, an equilibrium solution
and concentric solutions, are the ones which
take part in a phase reaction. On the other
hand, a saturated solution is involved in the
Lever system. - 8.Which of the following is the formula for
condense phase rule?
a) F=C-P+2
b) F=C-P+1
c) F=C+P-2
d) F=C+P-1
Answer: b
Explanation: In a condensed phase rule
system, the phases are represented in three
dimension which is not suitable for graphic
purposes and hence the pressure is considered
to be zero (this is helpful in drawing 2D
images). Hence the formula reduces to F=CP+2. - 9.Calculate the eutectic concentration given
the following data.
Pressure= 1atm
Temperature: 1oC
a) 0
b) 2
c) 1
d) 3
Answer: c
Explanation: According to Weiss law (which
suits only for phase components),
concentration at equilibrium is C=T/P.
therefore in this case, C=1/1=1. This law is
also called as Gibbs relativity law.
- 10.Under what condition, will we get a stable
phase diagram?
a) Solid + Liquid
b) Solid + Vapor
c) Liquid + vapor
d) Liquid + Solid
Answer: a
Explanation: According to equilibrium
mixture ration, an appropriate ratio of 1:10
parts of solid and liquid along with an
aqueous solution will give a stable phase
product
THERMAL ANALYSIS AND COOLING CURVES
- 1.Thermal analysis is defined as
a) Measurement of concentration of materials
as a function of temperature
b) Measurement of solubility of materials as a
function of temperature
c) Measurement of physical properties as a
function of temperature
d) Measurement of line positions of crystals
as a function of temperature
Answer: c
Explanation: Thermal analysis is defined as
the measurement of physical and chemical
properties of materials as a function of
temperature. In practice, however the term
thermal analysis is used to cover certain
specific properties only. These are enthalpy,
heat capacity, mass and coefficient thermal
expansion. - 2.Which of the following method can be
used for the measurement of change in weight
of the oxysalts?
a) Thermoelectric analysis
b) Wagner analysis
c) Stockbarger analysis
d) Thermal analysis
Answer: d
Explanation: Measurement of change in
weight of the oxysalts and hydrates can be
achieved by thermal analysis as they
decompose on heating, In which we measure
the physical and chemical properties of the
materials. Wide range of materials can be
studied. - 3.What are the two main techniques for
thermal analysis?
a) FTG AND DGG
b) MSP AND FCT
c) TGA AND DTA
d) TSA AND DGF
Answer: c
Explanation: The two main thermal analysis
techniques are thermogravimetric analysis
known as TGA which measures the change in
weight with temperature and Differential
thermal analysis known as DTA which
detects changes in heat content. - 4.Dilatometry is also known as by which of
the following names?
a) TGA
b) DTA
c) DSC
d) TMA
Answer: d
Explanation: A fourth thermal analysis
technique is Dilatometry in which the change
in linear dimension of a sample as a function
of temperature is recorded. Recently it has
acquired a new name, thermomechanical
analysis (TMA). - 5.Which of the following statements given
below is false?
a) TGA, DTA and DSC are measured using same instrument.
b) TGA and DTA can be carried out
simultaneously.
c) TGA, DTA and DSC are measured using
different instruments.
d) TMA is a recent name of Dilatometry.
Answer: c
Explanation: With modern automatic thermal
analysis equipment it I possible to do TGA,
DTA and DSC using the same instrument,
with some models, TGA and DTA may be
carried out simultaneously. However, the
thermal analysis equipment is necessarily
rather complicated and expensive in order
that a wide variety of thermal events and
properties may be studied.
- 6.In thermogravimetric analysis, the result
obtained appear as a
a) Continuous chart
b) Continuous parabola
c) Continuous circular positions
d) Discontinuous chart
Answer: a
Explanation: Thermogravimetric is a
technique for measuring the change in weight
of a substance as a function of temperature or
time, the result usually appears a continuous
chart record, a schematic, typical, single step
decomposition reaction. - 7.What is the range of the rate in ◦Cmin-1
required during the heating process in TGA?
a) 1-20
b) 25-50
c) 100-200
d) 150-1000
Answer: a
Explanation: In the process of TGA
thermogravimetric technique, the sample
usually a few milligrams in weight, is heated
at a constant rate, typically in the range of 1-
20 ◦Cmin-1 and a constant weight Wi, until it
begins to decompose at temperature Ti. - 8.Under conditions of
heating, decomposition usually take place in
thermogravimetry. Fill up the suitable option
from the choices given below.
a) First order
b) Second order
c) Third order
d) Dynamic
Answer: d
Explanation: In thermogravimetric analysis
(TGA), decomposition usually take place
under dynamic heating conditions over a
range of temperature Ti to Tf and a second
constant weight plateau is then observed
above Tf, which corresponds to the weight of
the residue Wf. - 9.The Ti and Tf temperature depends on
which of the following factor?
a) Cooling rate
b) Mechanical property of the material
c) Thermal expansion coefficient
d) Atmosphere above the sample
Answer: d
Explanation: Initial and final temperature Ti
,Tf depends on variables such as heating rate,
the nature of the solid (e.g. its particle size)
and the atmosphere above the sample. The
effect of the atmosphere can be dramatic. - 10.What is the temperature required for the
decomposition of CaCO3 in degree Celsius?
a) 200
b) 500
c) 900
d) 1200
Answer: b
Explanation: The decomposition in the
thermogravimetric analysis of CaCO3 is
completed in vacuum at ~500◦C but in CO2 at
one atmosphere pressure, decomposition does
not even commence until above 900◦C. Ti, Tf
pertain to the particular experimental
conditions, therefore and do not necessarily
represent equilibrium decomposition
temperatures.
TWO COMPONENT SYSTEMS , LEAD-SILVER SYSTEM
- 1.What is the definition of a lower critical
temperature?
a) The minimum temperature at which
equilibrium is achieved
b) The lowest temperature at which two
components will attain vapor state
c) The lowest temperature at which two
components sublimates
d) The lowest temperature at which two
components form a mixture
Answer: a
Explanation: The lower critical solution
temperature is the lowest temperature at
which two components are insoluble and
attains equilibrium. Conversely, the upper
critical solution temperature is the highest
temperature at which two components are
soluble as single phase. - 2.With reference to a two component system,
a vapor line indicates
a) A region where the temperature and
pressure remains stable
b) A region where the solubility remains
constant
c) An area below which components do not
mingle
d) An area above which both the components
mingle to form a single mixture
Answer: a
Explanation: A vapor line is another name
for an isotherm. It represents constant
temperature and constant pressure relation at
which the equilibrium is obtained. A vapor
line helps in finding out equilibrium
concentrations. - 3.With reference to a two component system,
an isobar indicates
a) A region where the temperature remains
constant
b) An area below phase end products remains
c) An area above which only the liquid vapors
remains
d) A region where the composition lies in
equilibrium
Answer: d
Explanation: An isobar is a line that
indicates a region where the composition
remains constant and in the equilibrium state.
In a two component solid-liquid system, it is
drawn vertically covering a wide range of
temperatures. - 4.Which of the following statements is not
true for a system that has reached the eutectic
temperature?
a) The system is a open system
b) The system is a miscible fluid
c) Components lie in liquid state
d) A region between sublimation and eutectic
curve lies stable
Answer: a
Explanation: The eutectic temperature is
achieved by heating a liquid in the point
where the density of the liquid state is equal
to the density of the vapor state. Here, the
interface between the liquid and vapor
vanishes resulting in a miscible fluid. This
can only occur in a closed system (otherwise
the vapor would escape into the
surroundings). - 5.What does the term “ metastable” indicate?
a) A place where the composition of the
system remains constant
b) A place where the pressure remains
constant with low value
c) An area below which a vapor- liquid
mixture is obtained
d) A region where the temperature remains
constant
Answer: d
Explanation: A metastable is a line that
indicates a place where the temperature
remains constant. In a two component system
it is drawn horizontally covering a wide range
of compositions.
- 6.Which of the following statements are
correct about the equilibrium point on a two
component system?
a) All the compounds are liquid
b) The boiling point of the mixture is less
than the boiling points of the individual
compounds
c) The degree of freedom is 0
d) Invariant reaction takes place
Answer: b
Explanation: The Eutectic point on a phase
diagram is a point at which the mixture boils
at a temperature lower than that of the pure
substances. The substance attains equilibrium
state. - 7.During metastable state, the size of the particle
a) Increases
b) Decreases
c) Won’t change
d) Not related
Answer: a
Explanation: Since for a system to be in
equilibrium condition, its size automatically
increases by Mond’s effect which is why the
particle’s size increases during metastable
state due to changes in molecular size. - 8.Which of the following is not responsible
for phase deposition?
a) Container wall
b) Grain size
c) Stacking effect
d) Disjoints
Answer: a
Explanation: Under equilibrium conditions,
the molecules adhere to the center of the
container and under non-equilibrium
conditions, the vapors are let out through the
walls of the container hence the container
wall has no role to play in the reaction. - 9.Where does the particle growth occur?
a) Movement of grains
b) Movement of equilibrium liquid
c) Equilibrium mixture
d) Non equilibrium mixture
Answer: a
Explanation: During diffusion process in the
transformation of solid to vapor state, the
molecules move from regions of higher
concentration to regions of lower
concentrations and hence growth takes place
n a controlled way. - 10.Overall transformation rate changes with
temperature as follows under what condition?
a) Decreases
b) Increases then decreases
c) Follows a linear path
d) Increases with temperature
Answer: b
Explanation: According to the phase graph,
at the solidus region, the temperature is high.
As the melting point increases, the
temperature decreases and vice versa
(applicable to all component systems).
