Water is a weak electrolyte. Its $\Lambda^{0m}$ value can be determined with thehelp of Kohlrausch’s law. $\Lambda_{m}^{0}(\mathrm{HCl}) = \Lambda_{m}^{0}(\mathrm{H}^{+}) + \Lambda_{m}^{0}(\mathrm{Cl}^{-})$.......(i) $\Lambda_{m}^{0}(\mathrm{NaOH}) = \Lambda_{m}^{0}(\mathrm{Na}^{+}) + \Lambda_{m}^{0}(\mathrm{OH}^{-})$........ (ii)$\Lambda_{m}^{0}(\mathrm{NaCl}) = \Lambda_{m}^{0}(\mathrm{Na}^{+}) + \Lambda_{m}^{0}(\mathrm{Cl}^{-})$.......(iii)Adding (i) and (ii) and subtracting (iii) we get$\Lambda_{m}^{0}(\mathrm{H}_{2}\mathrm{O}) = \Lambda_{m}^{0}(\mathrm{H}^{+}) + \Lambda_{m}^{0}(\mathrm{OH}^{-})$$= \Lambda_{m}^{0}(\mathrm{HCl}) + \Lambda_{m}^{0}(\mathrm{NaOH}) - \Lambda_{m}^{0}(\mathrm{NaCl})$