The chapter “Thermodynamics” is a very important part of Chemistry in the syllabus of UPSEE examination. About 2-3 questions are always asked from this chapter in the examination.
In this article, engineering aspirants will get complete notes of chapter Thermodynamics including important concepts, formulae and previous years’ solved questions for UPSEE 2019.
Students can read the following topics here:
1. System and Surroundings,
2. Types of system (open, closed, isolated),
3. State variables/functions,
4. Thermodynamic processes (isothermal, adiabatic, isobaric, isochoric),
5. Sign conventions,
6. Extensive and Intensive properties,
7. Enthalpy and Entropy,
8. Gibbs free energy,
9. First law of thermodynamics,
10. Relationship between Cp and Cv,
11. Standard enthalpy of reactions,
12. Enthalpy changes during phase transformations,
13. Properties of enthalpy changes,
14. Hess's law of constant heat summation and
About the notes:
1. These revision notes are based on the latest syllabus of the examination.
2. These notes are prepared by Subject Experts of Chemistry after the detailed analysis of last few years' papers of UPSEE.
3. With the help of these notes aspirants will get complete overview of the chapter Thermodynamics.
4. These notes contain the crux of the chapter Thermodynamics.
The System and the Surroundings
- System: The part of universe in which observations are made is called system.
- Surroundings: It includes everything other than the system.
The Universe = The system + The surroundings
Types of the System
- Open System: Exchange of energy and matter occurs between system and surroundings
Mathematically, ΔE ≠ 0 and Δm ≠ 0
- Closed System: No exchange of matter is possible, but exchange of energy is possible
Mathematically, ΔE ≠ 0 and Δm = 0
- Isolated System: No exchange of energy or matter between the system and the surroundings is possible
Mathematically, ΔE = 0 and Δm = 0
State variables / State functions: The functions whose values depend only on the state of the system and not on how it is reached are called state functions.
- Isothermal Process: For isothermal process temperature is constant
Mathematically, ΔT = 0
- Adiabatic Process: For adiabatic process there is no exchange of heat with surrounding
Mathematically, q = 0
- Isobaric Process: It occurs at constant pressure
Mathematically, Δp = 0
- Isochoric Process: It occurs at constant volume
Mathematically, ΔV = 0
- Anything given to system is taken positive.
For ex: heat given to system or work done on system is taken as positive
- Anything taken out of system is taken negative.
For ex: heat given out by the system or work done by system is taken negative
Extensive and Intensive Properties
- Intensive property: This is a property whose value doesn’t depend on the quantity or size of matter present in the system.
Example: temperature, density, pressure
- Extensive property: This is a property whose value depends on the quantity or size of matter present in the system.
Example: mass, total volume
Standard enthalpy of reactions: It is the enthalpy change for a reaction when all the participating substances are in their standard states.
Enthalpy changes during phase transformations:
- Standard Enthalpy of Fusion: It is also called molar enthalpy of fusion and denoted as ΔfusH°. It is defined as enthalpy change that accompanies melting of one mole of a solid substance in standard state.
- Standard Enthalpy of vaporization: It is also called molar enthalpy of vaporization and denoted as ΔvapH°. It is defined as amount of heat required to vaporize one mole of a liquid at constant temperature and under standard pressure.
- Standard enthalpy of sublimation: It is denoted as ΔsubH°.It is defined as the change in enthalpy when one mole of a solid substance sublimes at a constant temperature and under standard pressure (1 bar).
- Standard enthalpy of formation: It is denoted as ΔfH°. It is defined as the standard enthalpy change for the formation of one mole of a compound from its elements in their most stable states of aggregation. It can be positive or negative.
- Standard enthalpy of combustion: It is denoted as ΔcH°. It is defined as the heat evolved when one mole of substance in standard state is oxidised completely. It is always negative.
Properties of Enthalpy Change:
- It is an extensive property.
- It is a state function.
- On reversing the chemical reaction the sign ΔH of also reverses.
Some previous years' solved questions are given below:
The criterion for spontaneity of any process the change in entropy is (ΔSsystem + ΔSsurrounding ) > 0
Hence, the correct option is (D).
Hence, the correct option is (c).
Hence, the correct option is (c).
Hence, the correct option is (a).
Hence, the correct option is (b).
These notes will help students to save their precious time while preparing for the examination. Some previous years’ solved questions are also given here to make students understand the concepts very clearly. The content given in these notes is presented in a very systematic manner which will help students to grasp all the concepts very easily and quickly.
Pick the right college for your Engineering