Question

The molar conductivities at infinite dilution of barium chloride, sulphuric acid and hydrochloric acid are $280,860\text{and}426Sc{m}^{2}mo{l}^{–1}$ respectively. The molar conductivity at infinite dilution of barium sulphate is _______$Sc{m}^{2}mo{l}^{–1}$ .
(Round off to the Nearest Integer).

Answer 1

Answer: 288
Kohlrausch law:
At infinite dilution, when all the interionic effects disappear and dissociation of electrolyte is complete, each ion makes a definite contribution towards equivalent conductance of the electrolyte irrespective of the nature of the ion with which it is associated.
Kohlrausch law of independent migration of ions:
${\Lambda }_m^0={\lambda }_{m^{+}}^0+{\lambda }_{m^{-}}^0$

${\Lambda }_m^0\left(BaC{l}_2\right)=280Sc{m}^{2}mo{l}^{–1}$

${\Lambda }_m^0\left(H_{2}S{O}_4\right)=860Sc{m}^{2}mo{l}^{–1}$

${\Lambda }_m^0\left(HCl\right)=426Sc{m}^{2}mo{l}^{–1}$

${\Lambda }_m^0\left(BaS{O}_4\right)=??$

${\Lambda }_m^0\left(BaS{O}_4\right)={\Lambda }_m^0\left(H_{2}S{O}_4\right)+{\Lambda }_m^0\left(BaC{l}_2\right)-2\times {\Lambda }_m^0\left(HCl\right)$

$=860+280–(2\times 426)$

${\Lambda }_m^0\left(BaS{O}_4\right)=288Sc{m}^{2}mo{l}^{–1}$