Question

The term infinite dilution refers to:

Answer 1

Infinite dilution is the state in which the solute concentration is considered to be zero and the activity coefficient to be unity. It is defined as a solution that contains so much solvent that the concentration does not change on adding more solvent to it.

Complete step by step answer:
- As per the definition, the concentration does not change on adding more solvent at infinite dilution. This means that at infinite dilution weak electrolytes dissociate as strong electrolytes. This results in the complete ionization of the electrolytes and there is no change in the concentration of the solution even after adding any amount of solvents. Thus, the degree of dissociation becomes one. At infinite dilution the electrolyte is $100\%$ ionized. The molar conductivity at infinite dilution is called limiting molar conductivity. In other words, when the concentration of the electrolyte is zero or approaches zero, then the molar conductivity is known as limiting molar conductivity.
- At infinite dilution the ions are far apart which nullifies the interionic effect and thus the interionic effect becomes zero. Thus the equivalent conductance of an electrolyte becomes constant as the number of ions reaches a maximum value.
- Therefore, at infinite dilution an electrolyte is $100\%$ ionized and the degree of dissociation becomes one for weak electrolytes. Thus, all interionic effects disappear.
The correct answer is option “A,B and C” .

Additional Information : The migration of an ion at infinite dilution is dependent on the nature of the solvent and on the potential gradient, but not on the other ions present. This law is called Kohlrausch’s law. The law states that equivalent conductivity of an electrolyte at infinite dilution is the sum of equivalent conductivities of cations and anions. This law helps in the determination of limiting molar conductivities of any electrolyte. Weak electrolytes have lower molar conductivities and lower degree of dissociation at higher concentrations.

Note: The concept of infinite dilution is used to analyze a substance’s dissolution nature in solvents. This principle is used to test the properties of solutions in varying chemical environments. Infinite dilution is applicable only to strong electrolytes. The degree of dissociation is also called the degree of ionization. Infinite dilution is a hypothetical state of a solution in which solute concentration is zero.