Class 11 Chemistry - CBSE
Equilibrium
The Chapter Equilibrium in Class 11 Chemistry explores reversible reactions where the rates of forward and backward reactions become equal. You will learn about chemical and ionic equilibria, Le Chatelier's principle, and how factors like temperature, pressure, and concentration affect equilibrium systems. The chapter covers the calculation of equilibrium constants (Kc and Kp), pH calculations, buffer solutions, and the solubility product of sparingly soluble salts. This is a foundational, highly conceptual physical chemistry chapter that regularly features in CBSE board exams through numerical problems and theoretical reasoning questions.
Start Learning FreeKey Concepts
Dynamic Equilibrium
A state in a reversible reaction where the rate of the forward reaction equals the rate of the backward reaction, and measurable properties remain constant.
Law of Chemical Equilibrium
It states that at a given temperature, the product of concentrations of the reaction products raised to their respective stoichiometric coefficients divided by the product of reactant concentrations is a constant.
Le Chatelier's Principle
If a stress (change in concentration, pressure, or temperature) is applied to a system at equilibrium, the system shifts in a direction that minimizes or relieves that stress.
Buffer Solutions
Solutions that resist drastic changes in pH when small amounts of an acid or a base are added to them.
Solubility Product (Ksp)
The product of the molar concentrations of the constituent ions of a sparingly soluble salt in its saturated solution, each raised to the power of its stoichiometric coefficient.
Important Formulas
Board Exam Info
In the CBSE Class 11 Chemistry examination, the Equilibrium chapter typically carries around 6 to 8 marks. Questions usually include a mix of 1-mark conceptual MCQs, 2-mark reasoning questions based on Le Chatelier's principle, and 3-to-5-mark numerical problems on pH calculation, buffer solutions, or finding equilibrium constants.
Frequently Asked Questions
What is the difference between Kc and Kp?
Kc is the equilibrium constant expressed in terms of molar concentrations, while Kp is expressed in terms of partial pressures for gaseous reactions.
Does a catalyst change the equilibrium position?
No, a catalyst speeds up both the forward and backward reactions equally, helping the system reach equilibrium faster without changing the equilibrium constant or composition.
Why does adding an inert gas at constant volume not affect equilibrium?
At constant volume, adding an inert gas increases the total pressure of the container, but it does not change the partial pressures or molar concentrations of the reacting species, so the equilibrium remains undisturbed.
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