JEE Mains and Advanced

Equilibrium constant (Kp and Kc)

• For gaseous reactions, use Kp. For reactions in solution, use Kc.
• Equilibrium constants are constant at a given temperature.
• The magnitude of the equilibrium constant indicates the extent to which the reaction proceeds.

Concentration units (mol/L, atm, etc.)

• Use the appropriate concentration units for the reaction being studied.
• Be careful when converting between units.

Temperature (in Kelvin)

• All temperature must be in Kelvin.
• The temperature dependence of the equilibrium constant is given by the van’t Hoff equation.

Reaction stoichiometry

• Use stoichiometry to determine the mole ratios of reactants and products.
• Stoichiometry can also be used to determine the limiting reactant.

Le Chatelier’s principle

• Le Chatelier’s principle states that a system at equilibrium will shift in the direction that counteracts a change in conditions.
• This can be used to predict the effect of changes in concentration, temperature, and pressure on the equilibrium position.

Solubility equilibrium

• Solubility equilibrium occurs when the dissolved solute and the undissolved solute are in equilibrium.
• The solubility product constant (Ksp) is the equilibrium constant for a solubility equilibrium.

Acid-base equilibrium

• Acid-base equilibrium occurs when an acid and a base react to form a conjugate acid and a conjugate base.
• The equilibrium constant for an acid-base equilibrium is the acid dissociation constant (Ka).

Redox equilibrium

• Redox equilibrium occurs when an oxidizing agent and a reducing agent react to produce an oxidized product and a reduced product.
• The equilibrium constant for a redox equilibrium is the redox equilibrium constant (Keq).

Free energy change (∆G)

• The free energy change of a reaction is a measure of the spontaneity of the reaction.
• A negative value of ∆G indicates a spontaneous reaction.
• The standard free energy change (∆G°) is the free energy change of a reaction under standard conditions.

Enthalpy change (∆H)

• The enthalpy change of a reaction is a measure of the heat absorbed or released by the reaction.
• A positive value of ∆H indicates an endothermic reaction.
• A negative value of ∆H indicates an exothermic reaction.

Entropy change (∆S)

• The entropy change of a reaction is a measure of the disorder of the system.
• A positive value of ∆S indicates an increase in disorder.
• A negative value of ∆S indicates a decrease in disorder.

CBSE Board Exams

Equilibrium constant (Kc only)

• For reactions in solutions, use Kc.

Concentration units (mol/L only)

• Use the mol/L concentration units.

Temperature (in Celsius)

• All temperature must be converted to Kelvin.

Reaction stoichiometry

• Use stoichiometry to determine the mole ratios of reactants and products.
• Stoichiometry can also be used to determine the limiting reactant

Le Chatelier’s principle

• Le Chatelier’s principle states that a system at equilibrium will shift in the direction that counteracts a change in conditions.
• This can be used to predict the effect of changes in concentration and temperature on the equilibrium position.

Solubility equilibrium

• Solubility equilibrium occurs when the dissolved solute and the undissolved solute are in equilibrium.
• The solubility product constant (Ksp) is the equilibrium constant for a solubility equilibrium.

Acid-base equilibrium

• Acid-base equilibrium occurs when an acid and a base react to form a conjugate acid and a conjugate base.
• The equilibrium constant for an acid-base equilibrium is the acid dissociation constant (Ka).

Redox equilibrium

• Redox equilibrium occurs when an oxidizing agent and a reducing agent react to produce an oxidized product and a reduced product.
• The equilibrium constant for a redox equilibrium is the redox equilibrium constant (Keq).

Free energy change (∆G only)

• The free energy change of a reaction is a measure of the spontaneity of the reaction.
• A negative value of ∆G indicates a spontaneous reaction.