Question

The molar conductivities at infinite dilution for sodium acetate, HCI and NaCl are 91 S cm² mol^-1, 425.9 S cm² mol^-1 and 126.4 S cm² mol^-1 respectively. The molar conductivity of acetic acid at infinite dilution is ______.

Options

• 390.5 S cm² mol^-1

• 530.9 S cm² mol^-1

• 300.5 S cm² mol^-1

• 930.5 S cm² mol^-1

Answer 1

The molar conductivities at infinite dilution for sodium acetate, HCI and NaCl are 91 S cm² mol^-1, 425.9 S cm² mol^-1 and 126.4 S cm² mol^-1 respectively. The molar conductivity of acetic acid at infinite dilution is 390.5 S cm² mol^-1.

Explanation:

Given, `∧_("m"(NaAc))^circ` = 91 S cm² mol^-1 

`∧_("m"(HCl))^circ` = 425.9 S cm² mol^-1 

`∧_("m"(NaCl))^circ` = 126.4 S cm² mol^-1 

Using Kohlrausch law, to find the molar conductivity of acetic acid.

`∧_("m"(HaC))^circ = lambda_("H"^+)^circ + lambda_("AC"^-)^circ`

`= lambda_("H"^+)^circ + lambda_("Cl"^-)^circ + lambda_("AC"^-)^circ + lambda_("Na"^+)^circ - lambda_("Cl"^-)^circ - lambda_("Na"^+)^circ`

`∧_("m"(HCl))^circ + ∧_("m"(NaAc))^circ - ∧_("m"(NaCl))^circ`

= (425.9 + 91.0 - 126.4) S cm² mol^-1

= 390.5 S cm² mol^-1