Ch 9Equilibrium — Class 11 Chemistry, concept-first.

Equilibrium is a state in which two opposing changes occur at exactly equal rates, so that no net change in the system is visible even though, at the microscopic level, matter continues to move betwee…

The same dynamic character seen in physical equilibria carries over, unchanged in principle, to chemical reactions.

While the idea of "equal opposing rates" explains why a reaction stops changing, it does not by itself say what the actual equilibrium concentrations will be.

Equilibria are classified according to how many physical phases the reactants and products occupy, because this directly determines which species must be written into the equilibrium-constant expressi…

For a purely gaseous equilibrium, concentration is not the only convenient way to describe how much of each species is present — partial pressure works equally well, since for an ideal gas pressure is…

An equilibrium mixture is not frozen forever — if the conditions under which it was established are disturbed, the system responds by shifting toward a new equilibrium position.

Substances whose aqueous solutions conduct electricity are called electrolytes, and they do so because they exist, at least partly, as freely mobile ions in solution.

Since a weak electrolyte sets up a genuine ionization equilibrium, its degree of ionization can be derived quantitatively from the ionization constant using an equilibrium (ICE) table, exactly as for…

Even the purest water conducts electricity very slightly, because water itself undergoes a tiny degree of self-ionization: (more precisely written with a second water molecule accepting the proton to…

Every weak acid has a characteristic ionization constant, , and every weak base its own , each defined exactly as for any equilibrium constant. For a weak acid , ; for a weak base , .

Acids that can donate more than one proton per molecule — dibasic acids such as and , or polybasic (or polyprotic) acids such as — do not release all of their protons in a single step.

A buffer solution is one that resists an appreciable change in pH when a small amount of a strong acid or a strong base is added to it, or when it is moderately diluted.

When an acid and a base neutralize each other, the salt produced is not automatically neutral in water — its aqueous behaviour depends on the relative strengths of the acid and base that formed it, th…

Many ionic salts — such as , and — are described as "insoluble," but this is only a matter of degree: a very small amount of every ionic solid does dissolve, establishing a genuine equilibrium between…

This chapter traced one continuous idea — equilibrium as a state of equal, opposing rates, dynamic rather than static — through an increasingly specific series of settings.