Thermodynamics Miscellaneous
- The Vander Waals equation of state is {P + (a / c²)} (v – b)= RT, where p is pressure, v is specific volume, T is temperature and R is characteristic gas constant. The SI unit of a is
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p + a both term should gave same unit since they are getting added v² ⇒ N = a 
kg 
² m² m3 ⇒ a (unit) = m6 .kg. m kg² s²m² = m5kg = m5 kg² s² kgs²
Correct Option: C
p + a both term should gave same unit since they are getting added v² ⇒ N = a kg ² m² m3 ⇒ a (unit) = m6 .kg. m kg² s²m² = m5kg = m5 kg² s² kgs²
- 2 moles of oxygen are mixed adiabatically with another 2 moles of oxygen in a mixing chamber, so that the final total pressure and temperature of the mixtures become same as those of the individual constituents at their initial states. The universal gas constant is given as R. The change in entropy due to mixing, per mole of oxygen, is given by
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Since, ∆Q = 0, therefore S = ∫ dQ = 0 T
Correct Option: B
Since, ∆Q = 0, therefore S = ∫ dQ = 0 T
- Water has a critical specific volume of 0.003155 m3/kg. A closed and rigid steel tank of volume 0.025 m3 contains a mixture of water and steam at 0.1 MPa. The mass of the mixture is 10 kg. The tank is now slowly heated. The liquid level inside the tank
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vc = 0.0031 m3 /kg
v2 = 0.025 = 0.0025 m3/kg 10
as (vc > v)
As heat is supplied the amount of st eam in mixture will decrease and pressure will increase, because volume of mixture is less than critical vol ume. The fi nal st at e wi l l move t owar ds saturated liquid line. Hence level of liquid in tank will rise.
Correct Option: A
vc = 0.0031 m3 /kg
v2 = 0.025 = 0.0025 m3/kg 10
as (vc > v)
As heat is supplied the amount of st eam in mixture will decrease and pressure will increase, because volume of mixture is less than critical vol ume. The fi nal st at e wi l l move t owar ds saturated liquid line. Hence level of liquid in tank will rise.
- Which combination of the following statements is correct?
P: A gas cools upon expansion only when its Joule-Thomson coefficient is positive in the temperature range of expansion.
Q: For a system undergoing a process, its entropy remains constant only when the process is reversible.
R: The work done by a closed system in an adiabatic is a point function.
S: A liquid expands upon freezing when the slope of its fusion curve on pressureTemperature diagram is negative.
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First law of thermodymnamics,
1. δ Q = dU + δ W
Adiabatic, δ Q = 0
dU = – δ W
Hence work acts as the point function.
2. Liquid expands upon freezing when the liquid is water. In case of water the slope of fusion curve is negative.Correct Option: A
First law of thermodymnamics,
1. δ Q = dU + δ W
Adiabatic, δ Q = 0
dU = – δ W
Hence work acts as the point function.
2. Liquid expands upon freezing when the liquid is water. In case of water the slope of fusion curve is negative.
- When wet steam flows through a throttle valve and remains wet at exit
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Throttling always takes place in direction of decreasing pressure
Hence we can say during throtting temperature also decreases quality increases.Correct Option: B
Throttling always takes place in direction of decreasing pressure
Hence we can say during throtting temperature also decreases quality increases.
