D3818 Pages: 2

a steam boiler. Find the increase in total entropy of the combined system of gas
and water and increase in unavailable energy due to irreversible heat transfer.
Assume that the gases are cooled from 1000°C to 500°C and all the heat from
gases goes to water without any losses. Take: cpg (for gas) = 1.005 kJ/kg K, hfg
(latent heat of steam at 200°C) = 1940.7 kJ/kg.

8 a) Explain the importance of the critical point during the phase change process of a (4) pure

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substance usinga P-v diagram.
b) A pressure cooker contains 1.5 kg of saturated steam at 5 bars. Find the quantity (6)
of heat that must be removed from the steam so as to reduce the quality steam to
60% dry. What would be the pressure and temperature of the steam at the new
state.
PART ^
Answer any four full questions, each carries 10 marks
a) What are the reasons for the deviation of the real gas behaviour from the ideal (4) gas
behaviour.
b) 5 kg of 02 has a volume of 4.5 m? at 110°C. Compute the change in pressure of (6)
the gas by using the Van der Waals’ equation compared to the ideal gas equation.
Assume a = 362850 Nm*/(kg-mol)? and b = 0.0423 m*/kg-mol.
a) State and explain Amagat's law of partial volumes of gas mixtures. (4) b) A vessel of 0. 5
ന capacity contains 0.5 kg of COzand 1 kg of air at 20°C. (6) Calculate :
i) The apparent molecular mass of the mixture ii)
The partial pressure of each constituent, and iii)
The total pressure in the vessel.
The gravimetric analysis of air is to be taken as 23.3% ‏د0۰‎ and 76.7% 142
a) Derive the first Maxwell’s equation from the fundamentals and hence derive the (6)
remaining three from the first one.
0) Derivethe law of corresponding state from Vander Waals equation of state. (4)
a) Derive the Clausius- Clayperon equation. What is its use? (5) b) Using Van der Waals
equation of state, derive an expression for the change in (5) specific heats at constant pressure
and constant volume.
a) Explain Joule-Thomson coefficient and Inversion curve. (5) b) A vessel contains a mixture
of 1 mole of റാ and 4 moles of airat 1 bar and (5) 20°C. Calculate for the mixture :
i) The masses of റാ, 02 and 142 ii) The percentage carbon content by
mass iii) The apparent molecular weight and the gas constant for the
mixture iv) The specific volume of the mixture.
The volumetric analysis of air can be taken as 21% oxygen and 79% nitrogen.
a) What is meant by the term enthalpy of formation? Give reason for the difference (4)
between the higher and lower heating values of a fuel.
b) What is equivalence ratio for combustion? Write down the balanced combustion (6)
equation with an equivalence ratio of 1.5.

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