Chemical equilibrium is the condition in which the concentrations of reactants and products do not vary any more in a chemical process. The rate of forward reaction equals the rate of backward reaction at equilibrium.
Physical and Chemical Processes
1. Combination Reactions
Two or more chemicals combine to produce a single compound in such reactions.
e.g.,\s2Mg + O2 → 2MgO
2. Decomposition Reactions
These are the reactions. When a chemical decomposes, two or more distinct compounds are produced.
e.g., PCI5 ⇔ PCI3 + CI2
Food digestion is a breakdown event as well.
3. Displacement Reactions
One element or group is displaced by another in these reactions. In actuality, these are redox reactions, such as
Zn(s) + H2SO4
4. Double Displacement or Metathesis Reactions
Precipitation reactions, neutralisation reactions, and other reactions in which two compounds react to generate two new compounds with no change in oxidation state.
AgNO3(aq) + NaCI(aq) + AgCl(s) + NaNO3(aq) + NaNO3(aq) + NaNO3(aq) + NaNO3(aq) + NaNO3(aq) + Na (aq)
There are several types of equilibrium:
Characteristics of Chemical Equilibrium
Equilibrium can be achieved from any direction.
Equilibrium is dynamic in nature, i.e., the response does not end at equilibrium.
At equilibrium, the concentrations of different species do not vary.
The presence of a catalyst has no effect on the equilibrium state. Catalyst aids in the speedy attainment of balance.
The process's observable physical features become constant.
Law of Mass Action
2SO3 = 2SO2(g) + O2(g) (g)
Fe3O4(s) + 4H2O(g) Fe3O4(s) + 4H2O(g) Fe3O4(s) + 4H2O(g) Fe3O4(s) + 4H2O(g) Fe (g)
Effect of Change of Concentration
Effect of Change in Pressure
Effect of Temperature
Effect of Addition of Inert Gas
(i) Under continual strain. if an inert gas is used as a filler It will boost the system's volume. As a result, the equilibrium will change in a direction where the number of moles of gases increases.
(ii) Constant-volume addition of inert gas An inert gas is introduced to maintain the volume of the system constant. The substance's relative molar concentration will not change. As a result, the reaction's equilibrium position is unaltered.
Effect of Catalyst
The presence of a catalyst has no effect on the equilibrium position. It just expedites the process of achieving balance.
Le-Chatelier’s Principle Applicable to Physical Equilibrium
(i) Pressure's effect on solubility: The solubility of gas will increase when pressure rises, and vice versa.
(ii) Solubility as a function of temperature: The absorption of heat causes some things to disintegrate. The solubility of such substances increases as the temperature rises and vice versa, as shown in the dissolution of NH4CI, KCI, KNO3, and other compounds. Calcium acetate and calcium hydroxide dissolve exothermically, therefore their solubility decreases as the temperature rises.
(iii) Pressure's effect on the melting point of ice:
Ice is a kind of liquid water.
Because ice has a larger volume than liquid water, greater pressure will cause ice to melt, according to the Le-Chatelier principle.