Question

Define ionic mobility? What is the unit of ionic mobility?

Answer 1

Hint : We can define ionic mobility as the ratio of ionic velocity to the potential gradient. Potential gradient is the potential difference applied at the electrodes divided by the distance between the electrodes. It is denoted by $\mu$ .

Complete Step By Step Answer:
Ionic mobility $\left( \mu \right)$ is the ability of charged particles to move through a medium in response to an electric field that is pulling them at a specified temperature and pressure. It is the drift speed acquired by the ions per unit applied electric field or potential gradient.
In simple words we can say that ionic mobility is the distance travelled by an ion per second under potential gradient of 1 volt per meter.
v $\alpha$ E ………..Where v = velocity of ion and E= applied electric field
v = $\mu$ E
Thus, $\mu = \dfrac{v}{E}$
Now, we’ll find a unit of ionic mobility.
$\mu = \dfrac{v}{E}$ = $\dfrac{{\dfrac{{metre}}{{\sec }}}}{{\dfrac{{volt}}{{metre}}}}$
Where, unit of v= metre per sec and unit of E= volt per metre
Thus, the unit of ionic mobility is;
$\mu = \dfrac{{metr{e^2}}}{{volt \times \sec }}$ = $metr{e^2}vol{t^{ - 1}}{\sec ^{ - 1}}$

Additional Information:
There are some factors that affect ionic mobility. Ionic mobility is inversely proportional to the size of ion. Large size ions have less ionic mobility. It is inversely proportional to the viscosity of solvent. Ionic mobility is also directly proportional to the temperature.

Note :
We have seen that ionic mobility $\left( \mu \right)$ is the velocity with which an ion moves under a potential gradient of one volt per cm. It is to be noted that $L{i^ + }$ has lowest ionic mobility in aqueous solution because it gets strongly hydrated and the size of hydrated ions is very large.