Ch 12Chemical Equilibrium — Class 11 Chemistry, concept-first.

Changes around us can be physical or chemical, and separately, reversible or irreversible. An irreversible change proceeds only in one direction until it is complete -- a natural waterfall, smoke spre…

Physical processes can reach equilibrium too, whenever they are carried out in a closed system. (a) Liquid-vapour equilibrium: when liquid water evaporates inside a sealed flask, water molecules escap…

A chemical reaction carried out in a closed system, so that neither reactants nor products can escape, often does not give a 100% yield of products -- some reactants remain once concentrations stop ch…

As any reaction proceeds, the concentration of each reactant falls while the concentration of each product rises.

The Law of Mass Action states that the rate of a chemical reaction at each instant is proportional to the product of the concentration terms of all the reactants, with each concentration raised to a p…

The chemical equilibrium is described mathematically in terms of the equilibrium constant, . Consider a hypothetical reversible reaction : since forward and reverse reactions occur simultaneously, rat…

For reactions involving gases, it is often more convenient to express the equilibrium constant in terms of equilibrium partial pressures rather than concentrations.

For a mixture of ideal gases, each component's partial pressure is directly proportional to its molar concentration at a fixed temperature.

Consider the general reversible gaseous reaction . Substituting , , and (Section 12.4.4) into the expression, , gives .

A homogeneous reaction is one in which every reactant and product is in the same phase, e.g. a gas-phase reaction such as .

The equilibrium constant has four defining characteristics. (1) Its value is independent of the initial concentrations of either the reactants or the products -- starting from any mixture, the same is…

The equilibrium constant has three main practical applications. (1) Predicting the direction of reaction: for , comparing the reaction quotient (Section 12.5) with tells us which way an unbalanced mix…

Le Chatelier's Principle states that when a system at equilibrium is subjected to a change (a stress) in any of the factors determining the equilibrium condition -- concentration, pressure, volume, or…

The Haber process is the industrial synthesis of ammonia gas from nitrogen and hydrogen gas, reacted in a fixed stoichiometric ratio by volume at a selected optimum temperature and pressure: .