Laws of Thermodynamics - Metallurgical Thermodynamics - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

In a three component system at constant pressure, the maximum number of phases that can coexist at equilibrium is

A

2

B

3

C

4

D

5

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2

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

Liquid steel is in equilibrium with a graphite crucible. The activity of carbon (with graphite as the reference state) in liquid iron is

A

0.5

B

0.85

C

1.0

D

1.5

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3

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

The configurational entropy, \(S_c\), in an ideal solid solution is given by: \(S_c = -R [x \ln x + (1-x) \ln(1-x)]\), where \(x\) is the mole fraction of solute. The limit of \(S_c\) as \(x\) tends to zero (\(\lim_{x \to 0} S_c\)) is

A

\(\infty\)

B

\(R \ln 2\)

C

\(R\)

D

\(0\)

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4

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

The standard free energy change for the reaction, \(2Fe(s)+\frac{3}{2}O_2(g)=Fe_2O_3(s)\), is \(0.258 T - 820.89 kJ mol^{-1}\), where \(T\) is the temperature in K. The approximate pressure for the dissociation of \(Fe_2O_3\) at 1100°C is

A

\(1.0x10^{-20}\) atm

B

\(1.46x10^{-12}\) atm

C

\(2.3x10^7\) atm

D

\(3.55x10^{-15}\) atm

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5

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

Enthalpy of formation at 298 K, \(\Delta H_f^o\) of \(CO_2\) and \(PbO\) are -393 kJ mol\(^{-1}\) and -220 kJ mol\(^{-1}\), respectively. The enthalpy change for the reaction \(2PbO + C \rightarrow 2Pb + CO_2\) is

A

-173 kJ

B

15 kJ

C

47 kJ

D

440 kJ

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6

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

When one mole of copper is quenched from 1000 K to 300 K, the amount of heat released is [Given: the specific heat capacity of copper in J K^-1 mol^-1 C_p = 22.68 + 6.3 × 10^-3 T, where T is temperature]

A

9.37 kJ

B

15.87 kJ

C

18.74 kJ

D

22.68 kJ

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7

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

The enthalpy change, ΔH^l→s, associated with the liquid-to-solid transformation at 900 K is

A

-9 kJ mol^-1

B

-10 kJ mol^-1

C

-12 kJ mol^-1

D

-15 kJ mol^-1

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8

2007 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2007

The entropy change, ΔS^l→s, associated with the liquid-to-solid transformation at 900 K is

A

4.97 J K^-1 mol^-1

B

0 J K^-1 mol^-1

C

-5.34 J K^-1 mol^-1

D

-8.95 J K^-1 mol^-1

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9

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

For a closed system of fixed internal energy and volume, at equilibrium

A

Gibb’s free energy is minimum

B

entropy is maximum

C

Helmholtz’s free energy is minimum

D

enthalpy is maximum

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10

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

The maximum number of phases in a quaternary system at atmospheric pressure are

A

2

B

3

C

4

D

5

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11

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

The intensive thermodynamic variables among the following are (P) pressure (Q) volume (R) temperature (S) enthalpy

A

P, Q

B

P, R

C

R, S

D

Q, R

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12

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

In a binary phase diagram, the activity of the solute in a two phase field at a given temperature

A

increases linearly with the solute content

B

decreases linearly with the solute content

C

remains constant

D

is proportional to the square root of the solute content

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13

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

For a regular solution A-B, \(\Delta H_B\) is 2660.5 J at \(x_B = 0.6\). The critical point of the miscibility gap in the system would be at

A

\(x_B = 0.5, T = 1000 K\)

B

\(x_B = 0.6, T = 1000 K\)

C

\(x_B = 0.5, T = 500 K\)

D

\(x_B = 0.6, T = 2000 K\)

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14

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

For Ni + 0.5O₂ = NiO, \(\Delta G^o = -250,000 + 100T\) Joules. At 1000 K, the \(p_{O_2}\) in equilibrium with Ni/NiO in atm is

A

\(2.13 \times 10^{-16}\)

B

\(8.54 \times 10^{-16}\)

C

\(1.46 \times 10^{-8}\)

D

\(2.92 \times 10^{-8}\)

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15

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

The melting point and latent heat of fusion of copper are 1356 K and 13 kJ mol^-1, respectively. Assume that the specific heats of solid and liquid are same. The free energy change for the liquid to solid transformation at 1250 K in kJ mol^-1 is

A

−4

B

−3

C

−2

D

−1

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16

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

According to the Clausius-Clapeyron equation, the melting point of aluminium

A

increases linearly with pressure

B

decreases linearly with pressure

C

increases exponentially with pressure

D

does not vary with pressure

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17

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

One mole of monoatomic ideal gas is reversibly and isothermally expanded at 1000 K to twice its original volume. The work done by the gas in Joules is

A

2430

B

2503

C

5006

D

5763

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18

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

In the Ellingham diagram C→CO line intersects M→MO line at temperature T1 and N→NO line at temperature T2. M and N are metals. T2 is greater than T1. The correct statements among the following are
(P) carbon will reduce both MO and NO at temperatures T > T2
(Q) carbon will reduce both MO and NO at temperatures between T1 and T2
(R) carbon will reduce both MO and NO at temperatures T < T1
(S) carbon will reduce MO but not NO at temperatures between T1 and T2
(T) carbon will reduce NO but not MO at temperatures between T1 and T2

A

P, S

B

Q, T

C

R, S

D

P, T

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19

2008 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2008

In a gaseous mixture, CO, CO₂ and O₂ are in equilibrium at temperature T. For the reaction CO + 0.5O₂ = CO₂, ΔG⁰ = -281,400 + 87.6T Joules. The correct statements among the following are
(P) The reaction will shift to left on increasing T
(Q) The reaction will shift to right on increasing T
(R) The reaction will shift to left on increasing pressure
(S) The reaction will shift to right on increasing pressure

A

P, S

B

P, Q

C

Q, R

D

R, S

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20

2009 · Metallurgical Engineering · Metallurgical Thermodynamics · Laws of Thermodynamics

Metallurgical Engineering (MT) 2009

Gibbs free energies of a system in states 1 and 2 are denoted by \( G_1 \) and \( G_2 \) respectively. The system will go spontaneously from state 1 to state 2, if and only if

A

\(G_1 - G_2 > 0 \)

B

\(G_1 - G_2 < 0 \)

C

\(G_1 - G_2 = 0 \)

D

\(G_1 < 0 \) and \(G_2 < 0 \)

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