The molar conductivity of a solution of a weak acid $\mathrm{HX}(0.01 \mathrm{M})$ is 10 times smaller than the molar conductivity of a solution of a weak acid HY $(0.10 \mathrm{M})$. If $\lambda_{\mathrm{X}^{-}}^0 \approx \lambda_{\mathrm{Y}^{-}}^0$, the difference in their $\mathrm{pK}_{\mathrm{a}}$ values, $\mathrm{pK}_{\mathrm{a}}(\mathrm{HX})-\mathrm{pK}_{\mathrm{a}}(\mathrm{HY})$, is (consider degree of ionization of both acids to be $\ll 1$ )