Grade 11
  1. Basic concepts of chemistry  1.1. Importance of Chemistry  1.2. Nature and scope of chemistry  1.3. laws of chemical combination  1.3.1. Law of conservation of mass  1.3.2. Law of definite proportions  1.3.3. Law of multiple proportions  1.3.4. Law of gaseous volume  1.3.5. Avogadro's Law  1.4. Dalton's atomic theory  1.5. Mole concept and molar mass  1.6. Percent composition  1.7. Empirical and molecular formula  1.8. Stoichiometry and Stoichiometric Calculations  1.9. Limiting reagent concept
  2. Structure of the atom  2.1. Discovery of the electron, proton, and neutron  2.2. Atomic Model  2.2.1. Thomson's model  2.2.2. Rutherford's model  2.2.3. Bohr's model  2.3. Quantum mechanical model of the atom  2.4. Dual nature of matter and radiation  2.5. Heisenberg's uncertainty principle  2.6. Quantum numbers  2.7. Atomic orbitals and their shapes  2.8. Electronic configuration of elements  2.9. Aufbau principle  2.10. Pauli's exclusion principle  2.11. Hund's maximum multiplicity rule  2.12. de Broglie's hypothesis  2.13. Photoelectric effect
  3. Classification of elements and periodicity in properties  3.1. Historical development of the periodic table  3.2. Modern Periodic Law and Periodic Table  3.3. Periodic trends in properties  3.3.1. Atomic and Ionic Radius  3.3.2. Ionization enthalpy  3.3.3. Electron gain enthalpy  3.3.4. Electronegativity  3.3.5. Valency  3.3.6. Metallic and Non-Metallic Properties  3.3.7. Oxidation states  3.4. Unusual Properties of the First Elements
  4. Chemical Bonding and Molecular Structure  4.1. Kossel–Lewis approach to chemical bonding  4.2. Ionic or electrovalent bond  4.3. Covalent bond and its features  4.4. Bond parameters  4.5. VSEPR Theory  4.6. Valence bond theory  4.7. Hybridization and its types  4.8. Molecular orbital theory  4.8.1. Bond order and stability  4.9. Hydrogen bonding
  5. States of matter  5.1. Intermolecular forces  5.2. Gas Laws  5.2.1. Boyle's law  5.2.2. Charles's Law  5.2.3. Avogadro's Law  5.2.4. Dalton's law of partial pressure  5.2.5. Graham's law of spread  5.3. Ideal Gas Equation and Applications  5.4. Real gases and deviations from ideal behaviour  5.5. Kinetic molecular theory of gases  5.6. Liquefaction of gases  5.7. Properties of Liquids  5.8. Surface tension and viscosity
  6. Thermodynamics  6.1. System and environment  6.2. Types of systems in thermodynamics  6.3. Types of procedures  6.4. First law of thermodynamics  6.5. Internal energy and enthalpy  6.6. Heat capacity and specific heat  6.7. Hess's law of constant heat summation  6.8. Bond dissociation enthalpy  6.9. Enthalpy of formation and combustion  6.10. Enthalpy of solution and neutralization  6.11. Spontaneity and the second law of thermodynamics  6.12. Gibbs free energy and its applications
  7. Balance  7.1. The concept of balance  7.2. Equilibrium constant and its applications  7.3. Le Chatelier's principle  7.4. Ionic equilibrium in solutions  7.5. Acid and Base Theory  7.5.1. Arrhenius concept  7.5.2. Bronsted-Lowry concept  7.5.3. Lewis concept  7.6. pH Scale and pOH  7.7. Common ion effect  7.8. Hydrolysis of salts  7.9. Buffer solutions and their mechanism of action  7.10. Solubility equilibrium of sparingly soluble salts
  8. Redox reactions  8.1. Oxidation and reduction concepts  8.2. Oxidation number and its applications  8.3. Redox reactions in terms of electron transfer  8.4. Balancing redox reactions (oxidation number and ion-electron methods)  8.5. Types of redox reactions  8.6. Electrochemical Cells and Redox Reactions
  9. Hydrogen  9.1. Position of Hydrogen in the Periodic Table  9.2. Isotopes of hydrogen  9.3. Preparation of Hydrogen  9.4. Properties of Hydrogen  9.5. Hydrides and their classification  9.6. Water and heavy water  9.7. Hydrogen peroxide and its properties  9.8. Uses of Hydrogen and Its Compounds
  10. S-block elements (alkali and alkaline earth metals)  10.1. Group 1 Elements - Properties and Trends  10.2. Group 2 Elements - Properties and Trends  10.3. Unusual properties of lithium and beryllium  10.4. Important compounds of sodium and their uses  10.5. Important Compounds of Magnesium and Calcium
  11. Some p-block elements  11.1. General Introduction to p-Block Elements  11.2. Group 13 Elements  11.2.1. Boron and its compounds  11.3. Group 14 Elements  11.3.1. Carbon and its allotropes  11.3.2. Important Compounds of Carbon and Silicon
  12. Organic Chemistry - Some Basic Principles and Techniques  12.1. Classification and Nomenclature of Organic Compounds  12.2. Structural representation of organic compounds  12.3. Classification of organic reactions  12.4. Electronic Effects in Organic Chemistry  12.4.1. Inductive effect  12.4.2. Resonance effect  12.4.3. Hyperconjugation  12.5. Reaction mechanism and intermediate species  12.6. Purification and qualitative analysis of organic compounds
  13. Hydrocarbons  13.1. Hydrocarbons  13.1.1. Preparation and Properties of Alkenes  13.2. alkene  13.2.1. Preparation and Properties of Alkenes  13.2.2. Electrophilic addition reactions  13.3. Alkynes  13.3.1. Preparation and Properties of Alkynes  13.4. Aromatic hydrocarbons  13.4.1. Structure and properties of benzene  13.4.2. Electrophilic substitution reactions of benzene
  14. Environmental Chemistry  14.1. Environmental Pollution  14.2. Atmospheric pollution and the greenhouse effect  14.3. Water pollution and treatment methods  14.4. Soil pollution and its effects  14.5. Industrial waste and its treatment  14.6. Strategies for pollution control

Grade 11 → Balance ↓


Buffer solutions and their mechanism of action


Understanding buffer solutions is a fundamental aspect of chemistry, especially in the area of chemical equilibrium. Buffers play a vital role in maintaining pH levels in various chemical and biological systems. This detailed article explains buffer solutions, how they work, and their relevance in chemical equilibrium in a detailed and simple manner. We will discuss in detail the components that make up buffer solutions, their mechanism of operation, and some examples illustrating their application.

What is a buffer solution?

A buffer solution is a special type of solution that resists changes in its pH value when small amounts of acid or base are added. This defining characteristic of a buffer solution is important in a variety of scientific applications, including biochemical systems where enzymes can only function optimally at specific pH levels.

Components of buffer solution

Buffer solutions typically contain a weak acid and its conjugate base or a weak base and its conjugate acid. This composition allows them to neutralize small amounts of added acid or base, keeping the pH of the system relatively constant. Let's look at these components with text examples and visualize them below.

Example of an acidic buffer

An acidic buffer solution can be composed of acetic acid (CH 3 COOH) and sodium acetate (CH 3 COONa). Here, acetic acid is the weak acid, and sodium acetate provides the conjugate base.

Acetic acid (CH3COOH) ⟷ acetate ion (CH3COO-) + H+
Sodium acetate (CH3COONa) ⟶ CH3COO- + Na+

Example of basic buffer

A basic buffer solution can be made from ammonia (NH 3) and ammonium chloride (NH 4 Cl). In this system, ammonia acts as the weak base, while ammonium chloride provides the conjugate acid.

Ammonia (NH 3) + H 2 O ⟷ NH 4+ + OH-
Ammonium chloride (NH4Cl) ⟶ NH4+ + Cl-

How do buffer solutions work?

Buffering action is primarily the result of two reversible reaction equilibria occurring in solution. This equilibrium is significantly affected by the presence of a weak acid and its conjugate base pair or a weak base and its conjugate acid pair.

Buffer action mechanism

The mechanism by which buffer solutions resist changes in pH can be illustrated by considering the addition of an acid or base to a buffer solution.

  • Adding acid to a buffer: If a small amount of a strong acid such as HCl is added to an acetic acid buffer, the conjugate base component of the buffer (acetate ion, CH 3 COO-) neutralizes the added hydrogen ions, forming more acetic acid. This conversion balances the extra acidity. 
    CH 3 COO- + H+ ⟶ CH 3 COOH
  • Adding base to buffer: If a small amount of a strong base such as NaOH is added to a buffer, the weak acid component neutralises the hydroxide ions by donating protons (H+), forming water and increasing the amount of conjugate base. 
    CH3 COOH + OH- ⟶ CH3 COO- + H 2 O

Henderson–Hasselbalch equation

An important formula used to calculate the pH of a buffer solution is the Henderson-Hasselbalch equation. This equation relates the pH of a buffer solution to the concentration of an acid and its conjugate base. The equation is given as:

pH = pK A + log 10 [A–] / [HA]

Here, pK a is the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.

This equation is used to estimate the pH of a buffer system. Let's look at an example involving acetic acid and sodium acetate:

If you have 0.1 M acetic acid and 0.1 M sodium acetate in a solution and you know that the pK of acetic acid is 4.76, you can calculate the pH as follows:

pH = 4.76 + log 10 (0.1 / 0.1)
    = 4.76 + log 10 (1)
    = 4.76 + 0
    = 4.76

Applications of buffer solutions

Buffer solutions are extremely important in a wide variety of applications. They are important in many chemical reactions, biological processes, and industrial applications.

  • Biological systems: Buffers are essential in biological functions, such as maintaining the pH balance of the blood. For example, human blood uses a bicarbonate buffer system to maintain a pH around 7.4, which is important for bodily functions.
  • Industrial applications: Buffers are used to maintain optimal conditions for chemical reactions in fermentation processes, dyeing of fabrics, and electroplating.
  • Pharmaceuticals: Many medications use buffers to ensure stability and proper absorption of the drug into the body.
  • Food industry: Buffer systems help control the acidity of foods and beverages, affecting taste and preservation.

Conclusion

Buffer solutions are an essential concept in the study of chemistry and play a vital role in maintaining equilibrium in both biological and chemical systems. By understanding the components and mechanisms of buffer solutions, one can appreciate their importance in a variety of scientific and industrial fields. This in-depth exploration into buffer solutions highlights the importance of these fascinating chemical systems in the natural and technological worlds.


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