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Equilibrium — Revision Notes

ICSE · Class 11 · Chemistry

Equilibrium revision notes for ICSE Class 11 Chemistry: 4 topics in quick points. Part of the ICSE Class 11 Chemistry syllabus.

81 questions38 flashcards9 formulas & key relations5 concepts

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A comparison illustrating why physical equilibrium (like liquid-vapor equilibrium) can only be achieved in a closed system, not an open one, due to the containment of matter.
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Key Topics to Revise

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1. Physical and Chemical Equilibrium

  • A large number of chemical reactions do not go to completion and attain a state of equilibrium after some time.
  • Equilibrium is dynamic: both forward and backward processes continue at the same rate.
  • The symbol for equilibrium is ⇌, read as reversible arrow.
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2. Henry's Law and Dissolution of Gases

  • Henry's Law was given by William Henry in 1803.
  • The mass of a gas dissolved in a given mass of solvent is proportional to the pressure of the gas at equilibrium, provided the gas does not undergo chemical change.
  • Henry's law applies only to ideal gases, or real gases at low pressure.
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3. Law of Mass Action, Equilibrium Constant, and Reaction Quotient

  • Law of mass action was given by Guldberg and Waage in 1864.
  • At constant temperature, the rate of a chemical reaction is directly proportional to the product of active masses of reacting species, each raised to its stoichiometric coefficient.
  • Equilibrium constant expresses the ratio of product active masses to reactant active masses at equilibrium.
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4. Types of Chemical Equilibria

  • Homogeneous equilibrium means all reactants and products are in the same phase.
  • Heterogeneous equilibrium means reactants and products are in different phases.
  • Examples of homogeneous equilibria include H2(g) + I2(g) ⇌ 2HI(g), 2SO2(g) + O2(g) ⇌ 2SO3(g), and CH3COOH(l) + C2H5OH(l) ⇌ CH3COOC2H5(l) + H2O(l).

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Full Notes

Key Concepts

Equilibrium in physical processes appearsA reversible reaction reaches chemical equilibriumAt constant temperatureKc is written using equilibrium concentrationsQ has the same form as

Frequently Asked Questions

What are the important topics in Equilibrium for ICSE Class 11 Chemistry?
Key topics in Equilibrium include Physical and Chemical Equilibrium, Henry's Law and Dissolution of Gases, Law of Mass Action, Equilibrium Constant, and Reaction Quotient, Types of Chemical Equilibria. Study these first, then practise questions on each for Class 11 exams.
How should I revise Equilibrium for Class 11 exams?
Learn the core ideas first, then work through the 81 practice questions on Equilibrium. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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