Wednesday, December 2, 2020

GATE Chemical Engineering Questions and Answers-Thermodynamics


In a vapour compression refrigerator system, designed to maintain an enclosure at -3C, the equipment are so sized that all heat transfer units realize an approach of 5C. Cooling water is available at 32C. What is the maximum possible COP?

(A)       5.9

(B)       6.2

(C)       6.7

(D)       7.1

                                                                                                                        GATE 1987

Answer:          (A)

 

Criterion of chemical equilibrium is that the total Gibb’s free energy change is

(A)       always positive

(B)       always negative

(C)       zero

(D)       not specifically defined

                                                                                                                 GATE 1988

    Answer:          (C)

 

Entropy is

(A)       intensive property

(B)       derived property

(C)       extensive property

(D)       None of the above

                                                                                                                        GATE 1989

Answer:         (C)

 

For gas and liquid phases in equilibrium a component in a non-ideal system follows the relation

GATE 1989


                                                                                                            GATE 1989

Answer:          (B)

 

The system liquid water in equilibrium with a mixture of water vapour and nitrogen has the following degrees of freedom

(A)       4

(B)       3

(C)       0

(D)       2

                                                                                                                        GATE 1990

Answer:          (D)

 

At 318 K at total pressure of 24.4 KPa, the composition of the system ethanol (1) ad toluene (2) at equilibrium is x1 = 0.3 and y1 = 0.64. The saturation pressure at the given temperature for pure components are P1 = 23.06 KPa and P2 = 10.05 KPa respectively. What is the value of GE/RT for the liquid phase?

(A)       0.41

(B)       0.51

(C)       0.58

(D)       0.62

                                                                                                            GATE 1991

Answer:          (A)

 

The binary mixture A – B forms an azeotrope with a boiling point of 71.8C at 1 bar pressure, the azeotropic composition being 55 mole percent A. The pure component vapour pressures at 71.8C are A = 0.710 bar; B = 0.743 bar. Estimate the activity coefficient of A with liquid, assuming the vapour to be an ideal.

(A)       1.40

(B)       1.56

(C)       1.61

(D)       1.68

                                                                                                                        GATE 1991

Answer:          (A)

 

For system in equilibrium at a given temperature and pressure

(A)       The entropy must be minimum

(B)       The enthalpy must be a minimum

(C)       The internal energy must be minimum

(D)       The Gibb’s free energy must be a minimum

                                                                                                                        GATE 1991

Answer:          (D)

 

The shape of T-S diagram for carnot cycle is

(A)       A rectangle

(B)       A rhombus

(C)       A trapezoid

(D)       A circle

                                                                                                            GATE 1991

Answer:          (A)

 

To obtained the integrated form of Claussius-Clapeyron equation

GATE 1991

from the exact Clapeyron equation, it is assumed that

(A)       The volume of the liquid phase is negligible compared to that of the vapour phase

(B)       The vapour phase behaves as an ideal gas

(C)       The heat of vaporization is independent of temperature

(D)       All the above are applicable

GATE 1991

Answer:          (D)

 

During Joule-Thomson expansion of gases

(A)       enthalpy remains constant

(B)       entropy remains constant

(C)       temperature remains constant

(D)       none of these

                                                                                                                        GATE 1992

Answer:          (A)

 

106 Jules of heat are transferred from a reservoir at 327C to an engine that operates an carnot cycle. The engine rejects heat to a reservoir at 27C. Determine the work done by the engine?

(A)       0.5×106 Joules

(B)       0.6×106 Joules

(C)       0.7×106 Joules

(D)       0.8×106 Joules

                                                                                                                        GATE 1992

Answer:          (A)

 

An inventor claims to have developed a refrigerator unit which maintains the refrigerated space at - 3C while operating in a room when the room temperature is 27C and which has a coefficient of performance of 9.5. How do you evaluate his claim?

(A)       Inventors claim is feasible

(B)       Inventor’s claim is not feasible

(C)       Insufficient data to evaluate his claim

(D)       None of these

                                                                                                                        GATE 1992

Answer:          (B)

 

For a single component, two phase mixture the number of independent variables are

(A)       2

(B)       1

(C)       0

(D)       3

                                                                                                                        GATE 1992

Answer:          (A)

 

The necessary and sufficient condition for equilibrium between two phases is

(A)       Concentration of each component should be same in the two components

(B)       The temperature of each phase should be same

(C)       The pressure should be same in two phases

(D)       The chemical potential of each component should be same in two phases

                                                                                                                        GATE 1992

Answer:          (D)

 

A rigid insulated cylinder has two compartments separated by a thin membrane while one compartment contains 1 kmol nitrogen at a certain temperature and pressure, the other contains 1 kmol of CO2 at the same temperature and pressure. The membrane is ruptured and the two gases are allowed to mix. Assume that the gases behave as ideal gases. Calculate the increase in entropy of the contents of the cylinder. Universal gas constant R = 8314 J/kmol.K.

(A)       11.53 KJ/K

(B)       12.52 KJ/K

(C)       13.25 KJ/K

(D)       14.51 KJ/K

                                                                                                                        GATE 1993

Answer:          (A)

 

In the vicinity of the triple point, the vapour pressure of liquid and solid ammonia, are respectively given by

GATE 1993

Where P in atm and T in K. What is the temperature at the triple point?

(A)       195 K

(B)       203 K

(C)       250 K

(D)       275 K

                                                                                                                        GATE 1993

Answer:          (A)

 

The relationship (∂T/∂P)H= 0 holds good for

(A)       an ideal gas at any state

(B)       a real gas at any state

(C)       any gas at its critical state

(D)       any gas at its inversion point

                                                                                                                        GATE 1993

Answer:          (A)

 

During the change of phase of pure substance

(A)       dG = 0

(B)       dP = 0

(C)       dH = 0

(D)       dV = 0

                                                                                                                        GATE 1993

Answer:          (A)

 

At the triple point of a pure substance, the number of degrees of freedom is

(A)       0

(B)       1

(C)       2

(D)       3

                                                                                                                        GATE 1993

            Answer:          (A)


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