Difference in ${\mathrm{\Lambda }}_{\mathrm{m}}^{\mathrm{o}}$ of KBr and NaBr is ‘X’ $\mathrm{mho}{\mathrm{cm}}^2{\mathrm{mole}}^{-1}$. Difference in ${\mathrm{\Lambda }}_{\mathrm{m}}^{\mathrm{o}}$KNO₃ and NaNO₃ is ‘Y’  $\mathrm{mho}{\mathrm{cm}}^2{\mathrm{mole}}^{-1}$. Correct relation between ‘X’ and ‘Y’ is

According to Kohlrausch,

“The contribution of an ion to the total molar conductance remains the same irrespective of the oppositely charged ion with which it is present in the electrolyte”.

(1) KBr and NaBr —--------cations are ${\mathrm{K}}^{+} \mathrm{and} {\mathrm{Na}}^{+}$ with a common anion Br^-

(2) ${\mathrm{KNO}}_3$ and ${\mathrm{NaNO}}_3$---- cations are ${\mathrm{K}}^{+} \mathrm{and} {\mathrm{Na}}^{+}$ with a common anion ${\mathrm{NO}}_3^{-}$

So the difference in ${\mathrm{\Lambda }}_{\mathrm{m}}^{\mathrm{o}}$ is only due to ${\mathrm{K}}^{+} \mathrm{and} {\mathrm{Na}}^{+}$ which remains the same in both cases.