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

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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9

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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10

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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11

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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12

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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13

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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14

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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15

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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16

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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17

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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18

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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19

2012 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2012

An insulated, evacuated container is connected to a supply line of an ideal gas at pressure \( P_s \), temperature \( T_s \) and specific volume \( v_s \). The container is filled with the gas until the pressure in the container reaches \( P_s \). There is no heat transfer between the supply line to the container, and kinetic and potential energies are negligible. If \( C_p \) and \( C_v \) are the heat capacities at constant pressure and constant volume, respectively (\( \gamma = C_p/C_v \)), then the final temperature of the gas in the container is

A

\(\gamma T_s \)

B

\(T_s \)

C

\((\gamma - 1) T_s \)

D

\((\gamma - 1) T_s / \gamma \)

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20

2013 · Chemical Engineering · Thermodynamics · Thermodynamic Laws and Properties

Chemical Engineering (CH) 2013

The thermodynamic state of a closed system containing a pure fluid changes from (T₁, p₁) to (T₂, p₂), where T and p denote the temperature and pressure, respectively. Let Q denote the heat absorbed (> 0 if absorbed by the system) and W the work done (> 0 if done by the system). Neglect changes in kinetic and potential energies. Which one of the following is CORRECT?

A

Q is path-independent and W is path-dependent

B

Q is path-dependent and W is path-independent

C

(Q – W) is path-independent

D

(Q + W) is path-independent

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