Class 11 Chemistry - ISC
Thermodynamics
The Chapter Thermodynamics in Class 11 Chemistry ISC syllabus introduces the study of energy changes accompanying chemical and physical processes. Students learn about system and surroundings, types of systems, and state functions. The core of the chapter covers the First Law of Thermodynamics (conservation of energy), enthalpy, internal energy, and Hess's Law of Constant Heat Summation. It also explores spontaneity through the Second Law, introducing entropy and Gibbs free energy. This chapter is vital for board exams, frequently featuring numerical problems on enthalpy changes, entropy, and Gibbs free energy calculations, carrying around 6 to 8 marks.
Start Learning FreeKey Concepts
System and Surroundings
A system is the specific part of the universe under thermodynamic observation, while the surroundings comprise everything else in the universe outside the system.
First Law of Thermodynamics
Energy can neither be created nor destroyed, only converted from one form to another, mathematically expressed as delta U = q + w.
Enthalpy (H)
Enthalpy is the total heat content of a system at constant pressure, where the change in enthalpy (delta H) determines whether a reaction is exothermic or endothermic.
Hess's Law of Constant Heat Summation
The total enthalpy change for a chemical reaction is the same, whether the reaction takes place in one step or in a series of multiple steps.
Gibbs Free Energy (G)
Gibbs free energy is the thermodynamic potential that measures the maximum reversible work doable by a system at constant temperature and pressure, determining spontaneity.
Important Formulas
Board Exam Info
In the ISC Class 11 Chemistry examination, Thermodynamics typically carries around 6 to 8 marks. Questions usually include direct numerical problems on calculating delta H, delta U, or Gibbs free energy, derivations of work done in expansion, and conceptual questions regarding spontaneity and entropy.
Frequently Asked Questions
What is the difference between state functions and path functions?
State functions (like pressure, volume, temperature, enthalpy) depend only on the initial and final states of a system, not on the path taken. Path functions (like heat and work) depend entirely on the specific path followed during the change.
How do we know if a reaction is spontaneous using Gibbs free energy?
A reaction is spontaneous when the change in Gibbs free energy (delta G) is negative. If delta G is positive, the reaction is non-spontaneous, and if it is zero, the system is at equilibrium.
Why is delta H used more often than delta U in chemistry laboratories?
Most chemical reactions in the laboratory occur in open containers at constant atmospheric pressure rather than at constant volume, making enthalpy change (delta H), which measures heat transfer at constant pressure, much more convenient to measure.
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