Equivalent conductivity of a weak acid HA at infinite dilution is 390 cm² eq^-1 . Conductivity of 1x 10^-3  N HA solution is 4.9 x 1 ^-5 S cm-^-1 Calculate the extent of dissociation and dissociation constant of the acid. 

Equivalent conductivity of 1 x 10^-3 N HA solution (A_M) = k/ normality.
${\mathrm{\lambda }}_{\mathrm{c}} = \frac{4.9\mathrm{x}{10}^{-5 }\mathrm{x}1000 }{1 \mathrm{x} {10}^{-3}} = 49 \mathrm{S} {\mathrm{cm}}^2 {\mathrm{eq}}^{-1}$
Equivalent conductance at infinite dilution (A₀ ) = 390 S cm² wq^-1 
Extent of dissociation = $\mathrm{\alpha } = \frac{{\mathrm{\lambda }}_{\mathrm{c}}}{{\mathrm{\lambda }}_0}= \frac{49}{390} = .126$
Dissociation constant of acid = $C{\alpha }^2 = 1 x 10{ }^{-3}{(0.126)}^2 = 1.5 x {10}^{-5}mol L^{-1}$