The Equilibrium Constant – Introductory Chemistry
Chemistry is a comprehensive subject that deals with chemical compounds, reactants, products, and concentration of the reactants. It also deals with matter and the substances of which matter is composed. Concentration, in chemistry measures of the relative proportions of two or more quantities in a mixture.
The amount of the chemical substance in the chemical species of a solution or quantity of a substance per unit volume of solution is known as Molar concentration. A solution with a concentration of 1 mol/Liter is said to be 1 molar represented as 1 M.
There exist a factor known as Van’t Hoff Factor which determines the ratio between the original concentration of particles generated when the substance is dissolved and the concentration of a substance as measured from its mass. Van’t Hoff Factor is names after the Jacobus Henricus van’t Hoff the Dutch chemist.
The van’ t Hoff factor is typically 1 for non-electrolytes dissolved in water. For maximum ionic compounds dissolved in water, the Van’t Hoff factor is directly proportional to the number of discrete ions in the substance and is valid only for ideal solutions.
Ion pairing is witnessed in the solution and when the ions are paired it is considered as a single particle. This process of Ion pairing is seen in all electrolyte solutions and is the main cause for the deviation from the van’t Hoff factor.
Van’t Hoff Factor is represented as ‘i’.
Example: Van’t Hoff factor of CaCl2 = 3
CaCl2(s) ==> Ca2+(aq) + 2Cl–(aq) (3 moles of particles) CaCl2=3
Since CaCl2 dissociates into one Ca2+ ion and two Cl– ions. However, some of these ions associate with each other in the solution, leading to a decrease in the total number of particles in the solution.
Effects of Association/Dissociation in the solution
- Association refers to the combining of two or more particles to form one entity.
Example: 2 particles is the dimerization of carboxylic acids when dissolved in benzene.
- Dissociation refers to the splitting of a molecule into multiple ionic entities.
Example: sodium chloride (NaCl) dissociates into Na+ and Cl– ions when dissolved in water.
C6H12O6(s) ==>C6H12O6(aq) (1 particle)
Hence, C6H12O6 =1
NaCl(s) ==> Na+(aq) + Cl–(aq) (2 moles of particles)
For the association of particles, ‘i’ can be obtained by below formula.
α= n (i-1}/(n – 1)
For the dissociation of particles, ‘i’ can be obtained by below formula.
i = 1 + (n – 1)α
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