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JNTU B.Tech II MATERIALS THERMODYNAMICS Previous Question Paper (September - 2021 - R18)
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Main
State first law of thermodynamics give its significance.
Answer
The First Law of Thermodynamics, also known as the law of conservation of energy, states that energy can neither be created nor destroyed, only transformed from one form to another. For a closed system undergoing a process, the change in internal energy is equal to the heat added to the system minus the work done by the system.
The significance of the first law includes:
- It establishes the concept of internal energy as a state function.
- It provides the basis for energy balances in engineering systems, allowing for the quantification of energy transformations.
- It demonstrates that perpetual motion machines of the first kind, which would produce work without energy input, are impossible.
Compare extensive and intensive properties? Give examples for each of them.
Answer
Thermodynamic properties are classified based on their dependence on the size or extent of the system.
| Property Type | Definition | Examples |
|---|---|---|
| Extensive Properties | Properties that depend on the total quantity of matter or the size of the system. They are additive. | Mass, Volume, Total Internal Energy, Enthalpy, Entropy |
| Intensive Properties | Properties that are independent of the size or amount of matter in the system. They are not additive. | Temperature, Pressure, Density, Specific Volume, Molar Concentration |
The distinction is critical because extensive properties can be converted into intensive properties by dividing by the total mass or number of moles (e.g., specific volume is volume per unit mass). If two systems are combined, extensive properties sum up, whereas intensive properties remain constant if the systems are in equilibrium.
Define Kirchoff’s law and discuss its importance with suitable example.
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Prove that Cp > Cv.
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Derive an equation for entropy of a system. How the equilibrium of a system can be defined based on entropy? Explain.
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Derive combined expression of 1st and 2nd law of thermodynamics in terms of internal energy and enthalpy.
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Derive the expression for efficiency of Carnot engine.
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Zinc melts at 420 °C and its standard entropy at 25 °C is 9.95 cal/deg/ mole. Calculate the standard entropy of Zinc at 750 °C. Heat of fusion of Zn at the melting point is Hf = 1.74 KCal/m. Given Data ΔS0298 = 9.95 Cal/d/m. Cp(Zn)solid = 5.35 + 2.40×10-3 T Cal/d/m. Cp(Zn)liquid = 7.50 Cal/d/m.
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Derive Gibb’s Helmholtz equation.
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Derive Maxwell’s relations.
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Derive the Clausius - Clapeyron equation.
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List out various types of equilibrium. Explain them in detail.
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Prove that when Henry’s law is obeyed by the solute, solvent obeys Raoult’s law.
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Differentiate between ideal solution and non-ideal solution.
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Explain about the C-CO and C-CO2 lines in the Ellingham diagram.
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Discuss the applications of Ellingham diagram in extraction of metals.
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