Chemical Thermodynamics Notes: Class 11 Chemistry Chapter 5
Class 11 Chemistry Chapter 5 Chemical Thermodynamics covers the basic thermodynamic terms, the first law of thermodynamics, enthalpy, Hess's Law, and spontaneity of processes (second law).
Overview of Topics & Subtopics (Click to Jump)
1. Basic Concepts of Thermodynamics
Short Note:
• A system is the part of the universe under study; the surroundings is everything else. Systems can be open, closed, or isolated depending on exchange of matter and energy.
• State functions (e.g. internal energy U, enthalpy H) depend only on the initial and final state, not on the path taken; path functions (e.g. heat q, work w) depend on the path.
2. First Law of Thermodynamics
Short Note:
• ΔU = q + w, i.e. energy can neither be created nor destroyed, only converted from one form to another (Law of Conservation of Energy applied to thermodynamics).
3. Enthalpy and Its Types
Short Note:
• Enthalpy (H) = U + pV; ΔH = ΔU + pΔV (at constant pressure), representing the heat absorbed or released in a process at constant pressure.
• Hess's Law of Constant Heat Summation: the total enthalpy change for a reaction is the same, regardless of the number of steps taken, as long as initial and final conditions are the same.
• Types include enthalpy of formation, combustion, neutralisation, atomisation, and bond enthalpy.
4. Spontaneity and Gibbs Energy
Short Note:
• Entropy (S) is a measure of the degree of randomness or disorder of a system; the Second Law states the total entropy of the universe increases in every spontaneous process.
• Gibbs Free Energy: ΔG = ΔH − TΔS. For a spontaneous process at constant T and p, ΔG < 0.