Choose the correct statement(s) about ionic mobility and transport number.

AFor a solution containing a single electrolyte, the transport numbers of the cation and the anion add up to 1
BThe transport number of a given ion has the same value in all its salts
CThe ionic mobility $u$ and the limiting molar ionic conductivity $λ^{\circ}$ of a singly charged ion are related by $u = λ^{\circ} / F$
DIn dilute HCl the transport number of $H X^{+}$ exceeds 0.8

Answer: A, C, D

Transport numbers are fractions of the total current, so

t_{+} + t_{-} = 1

for a single electrolyte: (A) is correct. The fraction depends on the counter ion as well:

t (K X^{+})

is about 0.49 in KCl but about 0.51 in

KNO X_{3}

, so (B) is wrong.

λ^{\circ} = z u F

gives

u = λ^{\circ} / F

for

z = 1

, so (C) is correct.

t (H X^{+}) = 349.8/ (349.8 + 76.3) = 0.82

, so (D) is correct.