Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II THERMODYNAMICS AND KINETICS Previous Question Paper (October - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
A stationary mass of gas is compressed without friction from an initial state of 0.35 m3 and 0.11 MPa to a final state of 0.25 m3 at constant pressure. There is a transfer of 48.67 kJ of heat from the gas during the process. How much does the internal energy of the gas change?
Answer
To determine the change in internal energy, we apply the first law of thermodynamics for a closed system: ΔU = Q - W, where Q is the heat transferred to the system and W is the work done by the system.
Given data:
Initial volume (V1) = 0.35 m3
Final volume (V2) = 0.25 m3
Pressure (P) = 0.11 MPa = 110 kPa
Heat transfer (Q) = -48.67 kJ (negative because heat is transferred from the gas)
The work done during a constant pressure process is calculated as:
Now, substitute the values into the first law equation:
The internal energy of the gas decreases by 37.67 kJ.
How do we know that the given system is in thermodynamic equilibrium? Explain the importance of thermodynamic equilibrium.
Answer
A system is in thermodynamic equilibrium when it simultaneously satisfies three conditions: mechanical equilibrium (no unbalanced forces or pressure gradients), thermal equilibrium (uniform temperature throughout the system and surroundings), and chemical equilibrium (no net change in chemical composition or mass transfer between phases). If any of these properties change over time, the system is not in equilibrium.
The importance of thermodynamic equilibrium lies in the fact that it provides a stable state where macroscopic properties like pressure, temperature, and volume are well-defined and constant. It serves as the fundamental reference state for applying thermodynamic laws and equations of state, allowing for the calculation of state functions such as internal energy, enthalpy, and entropy. Without the assumption of equilibrium, the path-dependent processes cannot be analyzed using classical thermodynamic relations.
What is the work done by an ideal gas when it expands reversibly and adiabatically from (P1, V1) to (P2, V2)?
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Derive the equation for the estimation of internal energy for the closed system using first law of thermodynamics.
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Two moles of mono-atomic ideal gas at 1 bar and 300 K and 53kJ of heat is transferred to gas as a result of which the gas expands and does 1.3 kJ of work against surroundings. Calculate the final temperature of gas if process is reversible.
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How do we estimate the heat transfer and work transfer for the reversible adiabatic process? Derive them.
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Ten kg of water at 45°C is heated at constant pressure of 15 bar until it becomes super heated vapour at 400°C. Find the changes in volume, enthalpy, internal energy and entropy.
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What is the significance of third law of thermodynamics? Explain based on its principle.
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From the third law of thermodynamics, derive the ΔS0 for the given chemical reaction.
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Show that the Kelvin Planck statement and Claussius statement of second law of thermodynamics are equal.
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Derive the Maxwells’ relations from the thermodynamic relations and discuss their applications.
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Derive ΔG0 = -RT ln k from the Gibbs free energy function and discuss the salient features.
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Differentiate between the terms molecularity and order of reaction for the chemical reaction processes. Also explain the significance.
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What is second order chemical reaction? How to estimate the half life period of second order reaction?
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