1. Chemical Equilibrium

Chemical equilibrium is a state in a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the concentrations of reactants and products. At equilibrium, the system appears static macroscopically but is dynamic microscopically. Le Chatelier's principle describes how a system at equilibrium responds to changes in conditions (temperature, pressure, concentration), shifting to counteract the applied change and re-establish equilibrium.

2. Acids, Bases And Salts (Properties)

Acids are substances that typically donate protons (H$^+$) or accept electron pairs, and often taste sour. Bases typically accept protons or donate electron pairs, and often taste bitter or feel slippery. Salts are ionic compounds formed from the reaction of an acid and a base. Their properties, such as conductivity in aqueous solutions, pH, and reactivity, are crucial in understanding chemical behavior and are fundamental to many industrial and biological processes in India and worldwide.

3. Ionic Equilibrium in Solutions

Ionic equilibrium deals with the behavior of ions in aqueous solutions, particularly for weak electrolytes that partially dissociate. Concepts like degree of dissociation ($\alpha$) and equilibrium constants ($K_a$ for acids, $K_b$ for bases) describe the extent of ionization. The common ion effect states that the solubility of a sparingly soluble salt decreases if a soluble salt containing a common ion is added to the solution. Understanding ionic equilibrium is vital for pH calculations, buffer solutions, and solubility analysis.