Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II THERMODYNAMICS AND KINETICS Previous Question Paper (March - 2021 - R13)
Answer any five questions. All questions carry equal marks.
Main
Differentiate between reversible process and irreversible process and give the suitable examples.
Answer
A reversible process is an idealized process that occurs infinitely slowly, such that the system and surroundings remain in thermodynamic equilibrium at every stage. It can be reversed without leaving any trace on the surroundings. In contrast, an irreversible process occurs at a finite rate, involves dissipative effects like friction or unrestrained expansion, and results in a net increase in the entropy of the universe.
Examples of reversible processes include frictionless quasi-static expansion of a gas or a slow phase change at constant temperature and pressure. Examples of irreversible processes include spontaneous chemical reactions, heat transfer across a finite temperature difference, and the free expansion of a gas into a vacuum.
Two moles of mono-atomic ideal gas at 1.01325 bar and 298 K, in which a total amount of 82 J of heat is transferred to gas as a result of which the gas expands and does 1.9 kJ of work against surroundings. Calculate the final temperature of gas if process is reversible.
Answer
Given: n = 2 moles, T1 = 298 K, Q = 82 J, W = 1.9 kJ = 1900 J. For a mono-atomic ideal gas, the molar heat capacity at constant volume is Cv = 3/2 R.
Using the first law of thermodynamics: ΔU = Q - W
The change in internal energy for an ideal gas is given by:
Using R = 8.314 J/mol·K:
The final temperature of the gas is 225.11 K.
Derive the equation for the estimation of work transfer and heat transfer in a reversible adiabatic process.
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A stationary mass of gas is compressed without friction from an initial state of 0.375 m3 and 0.1025 MPa to a final state of 0.1573 m3 and pressure 0.5050 MPa during the process. There is a transfer of 82.6 kJ of heat from the gas during the process. Calculate polytropic index and also estimate the internal energy of the gas change.
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State and explain the Kelvin Planck statement of second law of thermodynamics.
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How do you obtain ΔS0 for a reaction? Explain the estimation from the third law of thermodynamics.
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Define and explain Helmholtz free energy function and Gibbs free energy function and discuss the applications of these functions.
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Explain the method for the estimation of change in entropy and quantification of irreversibility during the process.
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From the given values of Gibbs standard free energy changes of silica at 500°C, 1000°C and 1500°C, calculate its oxygen equilibrium pressures at these temperatures.
ΔG0500 = - 175000 Cal. mol-1
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ΔG01000 = - 153000 Cal. mol-1
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ΔG01500 = -131000 Cal. mol-1
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Derive the Claussius Clayperon equation for pure substance from the Maxwell’s relations and discuss its applicability.
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Apply the Gibbs phase rule for binary component system and discuss its importance.
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What are different methods to estimate the vapour pressure of an element? Explain them.
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Derive an expression for Raoult’s law for the solvent when Henry’s law is obeyed by the solute.
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What is meant by zero order and first order reactions? How they are different from second order reaction and how to determine the order of reaction?
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Suppose that the absolute rate of a certain process cannot be measured but the ratio of the rates r2/r1, at the two temperatures T2 and T1 can be measured. Find the activation energy of this process in terms of T2, T1 and r2/r1.
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