These notes for CBSE Class 11 Chemistry Chapter 7 cover the concept of equilibrium. It explains the equilibrium state where forward and reverse reaction rates are equal. The Law of Chemical Equilibrium is introduced, defining the equilibrium constant Kc based on molar concentrations and Kp based on partial pressures for gaseous reactions. The relationship Kp = Kc(RT)?n is provided. The notes discuss how the magnitude of Kc indicates the extent of a reaction. Le Chatelier's principle is explained as a method to counteract changes in equilibrium conditions. Various acid-base concepts including Arrhenius, Lewis, and Brønsted-Lowry definitions are presented, along with conjugate acid-base pairs. The ionic product of water (Kw), pH, pOH, pKa, and pKb are defined. Buffer solutions, the common ion effect, and salt hydrolysis are also detailed, classifying salts based on their acidic, basic, or neutral nature. These notes are ideal for revising key concepts for exams.
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? Equilibrium state- When rate of formation of a product in a process is in competition with rate of formation of reactants, the state is then named as “Equilibrium state”.
? Equilibrium in physical processes: ? Law of chemical equilibrium: At a given temperature, the product
of concentrations of the reaction products raised to the respective stoichiometric coefficient in the balanced chemicalequation divided by the
product ofconcentrations of the reactants raised totheir individual stoichiometric coefficientshas a constant value. This is known asthe Equilibrium Law or Law of Chemical Equilibrium.
aA +bB cC + dD |
|
| Kc =[C]c [D]d[A]a [B]b | |
| Chemical equation | Equilibrium constant |
| aA + b Bc C + D |
K) |
| cC + d Da A + b B |
K’ c=(1/Kc |
| na A + nb B ncC + ndD | K"" c= (Kcn) |
Concentrations or partial pressure of pure solids or liquids do not appear in the
expression of the equilibrium constant. In the reaction, KcAg2O(s) + 2HNO3M(aq) 2AgNO3
(aq)+H2O(l)
? If Qc >Kc, the reaction will proceed in the direction of reactants (reverse
reaction).If Qc <Kc, the reaction will proceed in the direction of the products
(forward reaction)
? Kp is equilibrium constant in terms of partial pressure of gaseous reactants and
products.
? Kc is equilibrium constant in terms of molar concentration of gaseous reactants and products
? Kp =Kc (RT)?n here R is gas constant, T is temperature at which theprocess is carried out &?n is no. of moles of gaseous product minus no. of moles of gaseous reactants.
? If Kc> 103; Kc is very high i.e. the reaction proceeds nearly to completion.
? If Kc<103; Kc is very small i.e. the reaction proceeds rarely.
? If Kcis ranging in the range of 103 to 10-3; i.e. reactants and products are just in equilibrium.
? ?Go = – RT lnK or ?Go = – 2.303RT log K
? Factors affecting equilibrium constant :- temperature, pressure, catalyst and molar concentration of reactants and products.
? L e Chate lie r ’s pr i nc i ple :- It states that a change in any of the factors that determine the equilibrium conditions of a system will cause the system to change in such a manner so as to reduce or toc ounteract the effect of the change.
? Arrhenius acids are the substances that ionize in water to form H+ . ? Arrhenius bases are the substances that ionize in water to form OH-.
? Lewis acids are lone pair (of e-) accepters while Lewis bases are lone pair donators.
? Proton donor are acids while proton accepters are bases(Bronsted-Lowry concept).
? The acid-base pair thatdiffers only by one proton is called a conjugateacid- base pair. IfBrönsted acid is a strong acid then itsconjugate base is a weak base and viceversa.
? Ionic product of water.Kw = [H+][OH–]
? pH = -log [H+] ; here[H+] is molar concentration of hydrogen ion.
?pH + pOH =14
?pKa + pKb =14
?Ka x Kb = Kw = ionic product of water=1 x 10-14
? Buffer solution :The solutions which resist change in pH on dilution or with the addition of small amounts of acid or alkali are called Buffer Solutions.
?common ion effect: It can be defined as a shift in equilibrium on adding a
substance that provides more of an ionic species already present in the dissociation equilibrium.
? Hydrolysis of Salts: process of interaction between water and cations an ions or both of salts is call edhydrolysis.
? The cations (e.g., Na+, K+,Ca2+, Ba2+, etc.) of strong bases and anions(e.g., Cl–, Br–, NO3–, ClO4– etc.) of strong acids simply get hydrated but do not hydrolyse, and therefore the solutions of salts formed from strong acids and bases are neutral i.e., theirpH is 7.
? Salts of weak acid and strong base e.g., CH3COON a are basic in nature.
? Salts of strong acid and weak base e.g.,NH4Cl, are acidic
? Salts of weak acid and weak base, e.g.,CH3COONH4. The pH is determined by the formula pH = 7 + ½ (pKa – pKb)
? Solubility product- product of the molar concentrations of the ions in a
saturated solution, each concentration term raised to the power equal to the no. of ions produced.
Chapter 7 part -1
Chapter 7 Part 2
An equilibrium state is reached when the rate of formation of products in a process equals the rate of formation of reactants.
It states that at a given temperature, the ratio of the product of concentrations of reactants raised to their stoichiometric coefficients is constant.
Kc is the equilibrium constant in terms of molar concentrations, while Kp is the equilibrium constant in terms of partial pressures of gaseous reactants and products.
Le Chatelier's principle states that if a change in conditions (like temperature, pressure, or concentration) is applied to a system at equilibrium, the system will shift to counteract that change.
Arrhenius acids ionize in water to form H+ ions, while Arrhenius bases ionize in water to form OH- ions.
A buffer solution resists changes in pH when small amounts of acid or alkali are added or upon dilution.
The pH is calculated using the formula pH = 7 + ½ (pKa – pKb).
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