Thermodynamic Laws and Properties - Thermodynamics - Chemical Engineering Previous Year Questions

1

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

The state of an ideal gas is changed from \((T_1, P_1)\) to \((T_2, P_2)\) in a constant volume process. To calculate the change in enthalpy, \(\Delta h\), ALL of the following properties/variables are required.

A

\(C_v, P_1, P_2\)

B

\(C_p, T_1, T_2\)

C

\(C_p, T_1, T_2, P_1, P_2\)

D

\(C_v, P_1, P_2, T_1, T_2\)

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2

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

The change in entropy of the system, \(\Delta S_{sys}\), undergoing a cyclic irreversible process is

A

greater than 0

B

equal to zero

C

less than zero

D

equal to the \(\Delta S_{surroundings}\)

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3

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

Parameters ‘a’ and ‘b’ in the van der Waals and other cubic equations of state represent

A

- molecular weight, b -- molecular polarity

B

- molecular size, b -- molecular attraction

C

- molecular size, b -- molecular speed

D

- molecular attraction, b -- molecular size

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4

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

For the two paths as shown in the figure, one reversible and one irreversible, to change the state of the system from a to b,

A

ΔU, Q, W are same

B

ΔU is same

C

Q, W are same

D

ΔU, Q are different

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5

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

For a pure substance, the Maxwell’s relation obtained from the fundamental property relation \( du = Tds - Pdv \) is

A

\((∂T/∂v)_s = - (∂P/∂s)_v \)

B

\((∂P/∂T)_v = (∂s/∂v)_T \)

C

\((∂T/∂P)_s = (∂v/∂s)_P \)

D

\((∂v/∂T)_P = - (∂s/∂P)_T \)

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6

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

Which of the following represents the Carnot cycle ( ideal engine ) ?

A

B

C

D

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7

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

2 kg of steam in a piston-cylinder device at 400 kPa and 175 °C undergoes a mechanically reversible, isothermal compression to a final pressure such that the steam becomes just saturated. What is the work, W, required for the process.
Data:
T = 175°C, P = 400 kPa → v = 0.503 m³/kg, u = 2606 kJ/kg, s = 7.055 kJ/kg-K
T = 175°C, satd. vapor → v = 0.216 m³/kg, u = 2579 kJ/kg, s = 6.622 kJ/kg-K

A

0 kJ

B

230 kJ

C

334 kJ

D

388 kJ

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8

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

A perfectly insulated cylinder of volume 0.6 m³ is initially divided into two parts by a thin, frictionless piston, as shown in the figure. The smaller part of volume 0.2 m³ has ideal gas at 6 bar pressure and 100 °C. The other part is evacuated.
At certain instant of time t, the stopper is removed and the piston moves out freely to the other end. The final temperature is

A

- 149 °C

B

- 33 °C

C

33 °C

D

100 °C

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9

2007 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2007

The cylinder insulation is now removed and the piston is pushed back to restore the system to its initial state. If this is to be achieved only by doing work on the system (no heat addition, only heat removal allowed), what is the minimum work required ?

A

3.4 kJ

B

107 kJ

C

132 kJ

D

240 kJ

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10

2008 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2008

Q.6 For a Carnot refrigerator operating between 40°C and 25°C, the coefficient of performance is

A

1

B

1.67

C

19.88

D

39.74

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11

2008 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2008

Q.7 The work done by one mole of a van der Waals fluid undergoing reversible isothermal expansion from initial volume \( V_i \) to final volume \( V_f \) is

A

\(RT \ln \left( \frac{V_f}{V_i} \right) \)

B

\(RT \ln \left( \frac{V_f - b}{V_i - b} \right) \)

C

\(RT \ln \left( \frac{V_f - b}{V_i - b} \right) - a \left( \frac{1}{V_f} - \frac{1}{V_i} \right) \)

D

\(RT \ln \left( \frac{V_f - b}{V_i - b} \right) + a \left( \frac{1}{V_f} - \frac{1}{V_i} \right) \)

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12

2009 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2009

An ideal gas at temperature \( T_1 \) and pressure \( P_1 \) is compressed isothermally to pressure \( P_2 (> P_1) \) in a closed system. Which ONE of the following is TRUE for internal energy (U) and Gibbs free energy (G) of the gas at the two states ?

A

\(U_1 > U_2, G_1 > G_2 \)

B

\(U_1 = U_2, G_1 < G_2 \)

C

\(U_1 > U_2, G_1 = G_2 \)

D

\(U_1 < U_2, G_1 = G_2 \)

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13

2009 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2009

The work required for compression (in kJ/mol) is

A

3.74

B

6.24

C

7.48

D

12.48

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14

2009 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2009

The final pressure \( P_2 \) (in bar) is

A

\(2^{5/4} \)

B

\(2^{5/3} \)

C

\(2^{3/2} \)

D

\(2^{5/2} \)

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15

2010 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2010

The Maxwell-Boltzmann velocity distribution for the x-component of the velocity, at temperature T, is \( f(v_x) = \sqrt{\frac{m}{2\pi kT}} \exp \left( -\frac{m v_x^2}{2kT} \right) \). The standard deviation of the distribution is

A

\(\sqrt{2kT/m} \)

B

\(kT/m \)

C

\(\sqrt{kT/m} \)

D

\(kT/2m \)

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16

2010 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2010

A saturated liquid at 1500 kPa and 500 K, with an enthalpy of 750 kJ/kg, is throttled to a liquid-vapour mixture at 150 kPa and 300 K. At the exit conditions, the enthalpy of the saturated liquid is 500 kJ/kg and the enthalpy of the saturated vapour is 2500 kJ/kg. The percentage of the original liquid, which vaporizes, is

A

87.5%

B

67%

C

12.5%

D

10%

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17

2011 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2011

One mole of methane is contained in a leak proof piston-cylinder assembly at 8 bar and 1000 K. The gas undergoes isothermal expansion to 4 bar under reversible conditions. Methane can be considered as an ideal gas under these conditions. The value of universal gas constant is 8.314 J mol\(^{-1}\) K\(^{-1}\). The heat transferred (in kJ) during the process is

A

11.52

B

5.76

C

4.15

D

2.38

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18

2012 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2012

In a throttling process, the pressure of an ideal gas reduces by 50 %. If \( C_p \) and \( C_v \) are the heat capacities at constant pressure and constant volume, respectively (\( \gamma = C_p/C_v \)), the specific volume will change by a factor of

A

2

B

\(2^{1/\gamma} \)

C

\(2^{(\gamma - 1)/\gamma} \)

D

0.5

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19

2012 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2012

If the temperature of saturated water is increased infinitesimally at constant entropy, the resulting state of water will be

A

Liquid

B

Liquid – vapor coexistence

C

Saturated vapor

D

Solid

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20

2012 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2012

In a parallel flow heat exchanger operating under steady state, hot liquid enters at a temperature \( T_{h,in} \) and leaves at a temperature \( T_{h,out} \). Cold liquid enters at a temperature \( T_{c,in} \) and leaves at a temperature \( T_{c,out} \). Neglect any heat loss from the heat exchanger to the surrounding. If \( T_{h,in} > T_{c,in} \), then for a given time interval, which ONE of the following statements is true?

A

Entropy gained by the cold stream is GREATER than entropy lost by the hot stream

B

Entropy gained by the cold stream is EQUAL to the entropy lost by the hot stream

C

Entropy gained by the cold stream is LESS than the entropy lost by the hot stream

D

Entropy gained by the cold stream is ZERO

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