Question

Give reason: Conductivity of $C{H_3}COOH$ decreases on dilution.

Answer 1

Conductivity is the conductance of unit volume of a solution. Conductance refers to the ease with which electric current flows through a material. Material which can conduct electricity is called conductors.

Complete step by step answer:
Conductivity is the ability to conduct electricity. Conductivity is also defined as the conductance of unit volume solution of an electrolyte.
Conductivity of any solution arises due to the movement of ions in that solution. Acetic acid ($C{H_3}COOH$) can dissociate to acetate ($C{H_3}CO{O^ - }$) and hydrogen ions (${H^ + }$). Thus conductivity of acetic acid arises due to the movement of acetate and hydrogen ions. But acetic acid is a weak acid. Hence its degree of dissociation is very small. Only a small fraction of acetic acid will be dissociated into acetate and hydrogen ions. Hence conductivity of acetic acid has a small value compared to other electrolytes such as HCl or NaCl.
Conductivity is directly proportional to the number of ions present per unit volume of the solution. When we dilute the acetic acid solution, its degree of dissociation increases. But the number of ions present per unit volume of the solution decreases. Hence conductivity also decreases. Therefore the reason behind decrease in conductivity on dilution is the decrease in number of ions per unit volume.

Note:
Conductivity is also known as specific conductance. Hence we can say that specific conductance decreases with dilution. But molar conductance increases on dilution. This is because of the increase in mobility of ions for strong electrolytes and increase in number of ions for weak electrolytes. We should not confuse between the terms specific conductance and molar conductance. Both are different.