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 ↓


Hydrolysis of salts


Chemistry is a fascinating subject that explains the nature and behavior of substances. An interesting phenomenon is the process of hydrolysis of salts. Understanding the concept of salt hydrolysis is important for explaining many chemical processes and equilibria in nature and industry.

What is hydrolysis?

Hydrolysis literally means "reaction with water." In chemistry terms, it refers to the process in which water reacts with a compound to break it down into other substances. When we talk about the hydrolysis of salts, we mean the chemical reaction that occurs when salt dissolves in water, often forming acidic or alkaline solutions.

Introduction to salts

Salts are ionic compounds composed of positively charged ions called cations, and negatively charged ions called anions. These ions can arise from acids and bases. For example, sodium chloride (NaCl) is a salt composed of sodium ions (Na +) and chloride ions (Cl -).

General equation for salt formation:

Acid + Base → Salt + Water

Types of salt hydrolysis

When salts dissolve in water, they can undergo hydrolysis, which can cause a change in the pH level of the solution. The nature of the ions present in the salt determines whether the solution becomes acidic, alkaline, or neutral.

1. Salts of strong acids and strong bases

Salts formed from strong acids and strong bases, such as NaCl (sodium chloride), usually do not undergo hydrolysis. This is because both the cation and the anion are stable and do not react with water. Therefore, the solution remains neutral with a pH around 7.

2. Salts of weak acids and strong bases

Consider the salt sodium acetate (CH 3 COONa). It is derived from the weak acid acetic acid (CH 3 COOH) and the strong base sodium hydroxide (NaOH).

When CH 3 COONa dissociates in water, the acetate ion (CH 3 COO - can react with water, producing hydroxide ions (OH -):

CH3COO - + H2O ⇌ CH3COOH + OH -

This process results in an alkaline solution having a pH value greater than 7.

3. Salts of strong acids and weak bases

Ammonium chloride (NH 4 Cl) is an example of a salt formed from the strong acid hydrochloric acid (HCl) and the weak base ammonia (NH 3).

With ammonium chloride, the ammonium ion (NH 4 +) undergoes hydrolysis:

NH 4 + + H 2 O ⇌ NH 3 + H 3 O +

The presence of H 3 O + ions shifts the pH towards the acidic side, so the solution is acidic and has a pH value less than 7.

4. Salts of weak acids and weak bases

Salts obtained from weak acids and weak bases have a more complex behavior. These salts (eg, ammonium acetate (CH 3 COONH 4)) can be hydrolyzed on both the cation and anion sides.

Depending on K_a and K_b values of the original acid and base, the solution may be acidic, basic, or neutral.

Chemical equilibrium in hydrolysis

Chemical equilibrium plays an important role in the dissolving of salts. At equilibrium, the rate of the forward reaction (dissociation of ions in water) is equal to the rate of the reverse reaction (recombination of ions).

Consider the hydrolysis of sodium acetate. In solution, the following dynamic equilibrium is established:

CH3COO - + H2O ⇌ CH3COOH + OH -

The position of this equilibrium can be affected by changes in concentration, temperature, or pressure, as determined by Le Chatelier's principle.

Factors affecting salt hydrolysis

Several factors can affect the extent of hydrolysis in a solution:

Presence of excess acid or alkali

Adding an external acid or base to a solution can shift the position of the equilibrium. For example, adding HCl to the hydrolysis mixture of sodium acetate will shift the equilibrium to the left, suppressing hydrolysis and reducing the concentration of OH - ions.

Effect of ion concentration

According to Le Chatelier's principle, increasing the concentration of one of the ions involved in the equilibrium can alter the reaction. For example, adding sodium ions can decrease the extent of acetate ion hydrolysis.

Example of hydrolysis with visual representation

To understand how hydrolysis works, consider a beaker with a salt solution. Below is a schematic representation:

beaker with salt solution Na + CH 3 COO -

Practical applications

Understanding salt hydrolysis is important both theoretically and practically. Here are some examples:

Buffer

Hydrolysis plays an important role in creating buffer solutions, which are solutions that can resist changes in pH when small amounts of acid or base are added. For example, the acetate ion from sodium acetate acts as a buffer in blood and other biological systems.

Soil chemistry

The acidity or alkalinity of the soil can be affected by the hydrolysis of salts present in it. This affects the availability of nutrients for plants and agricultural productivity.

Examples for practice

Here are some questions to test your understanding:

  1. When potassium chloride (KCl) is dissolved in water, predict the pH of the solution.
  2. Identify whether Nh 4 NO 3 solution in water is acidic, basic or neutral.

Conclusion

The hydrolysis of salts is a fundamental concept in chemistry that helps us understand how compounds react with water and how it affects their behavior and properties. This understanding is essential for explaining a variety of natural and industrial processes. By analyzing the hydrolysis of salts, we gain information about the balance of ions in the solution and how this affects the pH level and the overall chemical balance.


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Hydrolysis of salts

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