Thermodynamic Equilibria and Phase Diagrams - Thermodynamics, Kinetics and Phase Transformations - Engineering Sciences Previous Year Questions

1

2007 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2007

In a binary system A–B at one atmosphere, the parameter(s) that can be independently varied in the two phase (α+β) region is(are)

A

composition of α-phase as well as temperature

B

composition of α-phase as well as composition of β-phase

C

either composition of α-phase or composition of β-phase or temperature

D

only temperature

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2

2008 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2008

At constant pressure, the maximum degrees of freedom in a binary phase diagram are

A

0

B

1

C

2

D

3

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3

2008 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2008

In an alloy system, X-Y, three phases α (10), γ (21), and Liq. (45) are in equilibrium at 700°C and γ (21), Liq. (68) and β (89) are in equilibrium at 420°C. (numbers in the brackets are compositions of the phase in wt% of X). Choose the INCORRECT statement:

A

γ is an intermetallic compound

B

Equilibrium at 700°C is peritectic

C

Equilibrium at 420°C is eutectic

D

Equilibrium at 420°C is eutectoid

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4

2009 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2009

Steel containing 0.8 % carbon cooled under equilibrium conditions from molten state to room temperature is soft, because it consists of lamellae of

A

Ferrite and cementite

B

Ferrite and austenite

C

Ferrite and bainite

D

Ferrite and martensite

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5

2010 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2010

Match the terms in Column I with the details of phase transformations in Column II (→ indicates cooling)

A

P. eutectic, Q. monotectic, R. eutectoid, S. peritectic

B

1. L + α → β, 2. γ → α + β, 3. L → α + β, 4. α + β → γ, 5. L1 → α + L2

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6

2011 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2011

A plain carbon steel was annealed just above the eutectoid temperature. Microstructural analysis revealed that the proeutectoid ferrite content was 30 wt%. The eutectoid reaction in the iron-iron carbide phase diagram is given below: \[ \gamma \, (0.76 \text{ wt\% C}) \xrightarrow[\text{heating}]{\text{cooling}} \alpha \, (0.022 \text{ wt\% C}) + \text{Fe}_3\text{C} \, (6.7 \text{ wt\% C}) \] The carbon content of the steel (in wt%) is

A

0.24

B

0.34

C

0.44

D

0.54

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7

2012 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2012

During cooling from 900°C to 723°C, the proeutectoid α forms from γ. Find the volume % of proeutectoid α just below 723°C for the steel.

A

44.9%

B

66.1%

C

55.1%

D

34.9%

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8

2012 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2012

Find the volume % of pearlite for the steel just below 723°C for 0.45 wt.% carbon steel.

A

44.9%

B

55.1%

C

40.9%

D

59.1%

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9

2013 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2013

At a constant atmospheric pressure, the number of phases, P which coexist in a chosen system at equilibrium, is related to the number of components, C in the system and the degree of freedom, F by

A

P+F=C-2

B

P+F=C+2

C

P+F=C+1

D

P+F=C-1

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10

2013 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2013

What is the weight percentage of A in solid phase at this temperature?

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11

2013 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2013

What weight percentage of this alloy is liquid?

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12

2014 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2014

Match the reaction in Column I with its name in Column II.
L – liquid, α, β, γ – different solid solution phases

Column I	Column II
(P) L --cooling--> α + β	(1) peritectic
(Q) L + β --cooling--> γ	(2) eutectic
(R) α --cooling--> β + γ	(3) monotic
	(4) eutectoid

A

P-1, Q-4, R-3

B

P-2, Q-1, R-4

C

P-2, Q-3, R-1

D

P-4, Q-2, R-3

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13

2014 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2014

Which among the following rules need to be satisfied for obtaining an isomorphous phase diagram in a binary alloy system?
(P) The atomic size difference should be less than 15%.
(Q) Both the end components should have the same crystal structure
(R) The valency of the end components should be the same.
(S) The end components should have dissimilar electronegativities

A

P, Q, R

B

Q, R, S

C

R, S, P

D

S, P, Q

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14

2014 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2014

Relevant portion of a binary phase diagram of elements A and B is shown below. The mass fraction of liquid phase at 1000 °C for an alloy with 15 wt.% B is __________.

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15

2015 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2015

The eutectic reaction is
[Note: S – solid, L – liquid]

A

\(S_1 \rightleftharpoons S_2 + S_3\)

B

\(L \rightleftharpoons S_1 + S_2\)

C

\(L_1 + S_1 \rightleftharpoons L_2 + S_2\)

D

\(L_1 + S_1 \rightleftharpoons S_2 + S_3\)

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16

2016 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2016

Which of the following thermodynamic properties shows a discontinuity during a second-order phase transition?

A

Volume

B

Enthalpy

C

Entropy

D

Heat capacity

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17

2016 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2016

At equilibrium, the maximum number of phases that can coexist in a ternary system at constant pressure is _____________.

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18

2016 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2016

A half cell consisting of pure Ni immersed in an aqueous solution containing Ni\(^{2+}\) ions of unknown concentration, is galvanically coupled with another half cell consisting of pure Cd immersed in a 1 M aqueous solution of Cd\(^{2+}\) ions. The temperature is 25 °C and pressure is 1 atm. The standard electrode reduction potentials of Ni and Cd are \(-0.250\) V and \(-0.403\) V, respectively. The voltage of the cell is found to be zero. The concentration of Ni\(^{2+}\) in the solution is __________ \(\times 10^{-6}\) M.
(Given: Universal gas constant, \( R = 8.31 \) J K\(^{-1}\) mol\(^{-1}\), Faraday's constant, \( F = 96500 \) C mol\(^{-1}\))

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19

2016 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2016

For phase change from solid (sol) to liquid (liq) state, if the slope of the solid-liquid coexistence line in the $P$-$T$ diagram is negative, then:

A

$v_{liq} < v_{sol}$

B

$v_{liq} > v_{sol}$

C

$s_{liq} < s_{sol}$

D

$h_{liq} < h_{sol}$

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20

2017 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Thermodynamic Equilibria and Phase Diagrams

Engineering Sciences (XE) 2017

Refer to the figure below:

If the alloy contains 47 wt. % of A and 53 wt. % of B at 1300 °C, the wt. % of liquid present in the alloy at this temperature will be ……..

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