Deck 7: Thermodynamics

Question 1

During a polytropic expansion 25% of heat is converted into work while temperature of gas rises by 30 K, the specific heat of gas at constant volume is

A)10% w
B)12 % w
C)15% w
D)20% w

Answer 1

12 % w

Question 2

During a constant pressure expansion of a gas 33.3 % heat is converted into work while the temperature rises by 20K. The specific heat of gas at constant pressure is

A)10% w
B)12 % w
C)15% w
D)20% w

Answer 2

15% w

Question 3

During an adiabatic compression when temperature increase by 100% the pressure increases by 1000%. The ratio of specific heats, ? is

A)1.3
B)1.35
C)1.4
D)1.45

Answer 3

1.4

Question 4

The area under the curve on temperature entropy diagram represents

A)work done during the process
B)heat exchanged during the process
C)change in internal energy during the process
D)change in entropy during the process

Question 5

The change in entropy is zero during

A)hyperbolic process
B)constant pressureprocess
C)adiabatic processes
D)polytropic process

Question 6

Choose incorrect statement

A)isentropic process is adiabatic
B)adiabatic process has no heat exchange
C)hyperbolic process is isothermal
D)no work is done in constant pressure process

Question 7

Choose the correct statement

A)there is no change of entropy in an adiabatic expansion
B)entropy is an extensive property of gas derived from first law of thermodynamics
C)the area under the curve in a temp.-entropy diagram gives the change of entropy
D)the change of entropy during a constant pressure process is always negative

Question 8

1.6 Kg of air is expanded at constant pressure from 100°C to 0°C resulting in entropy change of - 2.0 J/K 3.2 Kg of air is cooled at constant volume from 100°C to 0°C with a change in entropy of -3.0 J/K. The ratio Cp/ Cv is

A)1.333
B)1.366
C)1.4
D)1.43

Question 9

Entropy at absolute zero temperature is zero for a

A)perfect gas
B)perfect substance
C)perfect crystal
D)glass

Question 10

The third law of thermodynamics

A)defines entropy
B)provides a base from which entropy is measured
C)defines change of entropy
D)gives availability of heat for conversion into work

Question 11

Entropy is called the property of a system because

A)it has same value at any two equilibrium states
B)it depends upon the process path
C)it has a unique value at each equilibrium state
D)it does not change between two equilibriumstates

Question 12

Entropy of mixture of two gases after sudden mixing is

A)greater than
B)less than its inputtemperature
C)same as sum of entropy ofindividual gases
D)unpredictable

Question 13

If a substance goes though a cycle of changes returning back to original state, the change in entropy is

A)positive
B)negative
C)zero
D)positive or negative depending upon originalstate

Question 14

A sequence of operations which a gas undergoes in such a way that final state is same as original state, mahe a

A)reversible cycle
B)irreversible cycle
C)thermal cycle
D)thermodynamic cycle

Question 15

In a reversible process

A)heat transfer takes place over finite temperaturedifference
B)heat transfer takes place over infinitesimaltemperature difference
C)heat transfer takes place from surrounding to thesystem
D)heat transfer takes place from the system tothe surrounding

Question 16

Which of the following processes is very close to reversible

A)lifting of a body above the ground
B)compression of a gas in the cylinder against a piston
C)flow of a fluid in a pipe
D)motion of a boat in water

Question 17

A perfect gas having p1= 0.1 M/mm², v1=0.18 m³, T1=20°C is compressed to 1/10 of volume in an isothermal process. The change in entropy is

A)-141.45 j/k
B)141.45 j/k
C)-41446.23 j/k
D)0

Question 18

The enthalpy of a system

A)i= internal energy + pv
B)i= internal energy + pdv
C)i= internal energy + vdp
D)i= change in internalenergy + pv

Question 19

Which statement is wrong for throttling expansion

A)pressure drop = 0
B)change in enthalpy = 0
C)work done = 0
D)change in internalenergy = 0

Question 20

Which statement is wrong for adiabatic expansion

A)h = 0
B)w = 0
C)ds = 0
D)w+e = 0

Question 21

Maximum amount of work that can be converted into heat in any process

A)depends upon initial & final temperature
B)depends upon how much work is lost in friction
C)is 50%
D)is 100%

Question 22

The universal gas constant will be equal to difference between specific heats at constant pressure & constant volume for

A)1 kg mass of gas
B)1 molecule of gas
C)1 kg molecule of gas
D)any mass of gas

Question 23

Air is compressed isothermally by performing work equal to 16 KJ upon it. The change in internal energy is

A)- 16 kj
B)zeroth law of thermodynamics
C)16 kj
D)32 kj