At `25^(@)C` molar conductance of `0.1` molar aqueous solution of ammonium hydroxide is `9.54 ohm^(-1) cm^(2) mol^(-1)` and at infinte dilution its molar conductance is `238 ohm^(-1) cm^(2) mol^(-1)` The degree of ionisation of ammonium hydroxide at the same concentration and termperature is

Options

A. `2.080%`
B. `20.800%`
C. `4.008%`
D. `40.800%`

Answer

C

Explanation

(c ) Given, molar conductance at 0.1 M concentration,
`lambda_(c)=9.54 Omega^(-1)cm^(2)mol^(-1)`
Molar conductance at infinite dilution,
`lambda_(c)^(oo)=238Omega^(-1)cm^(2) mol^(-1)`
We know that , degree of ionisation , `alpha=(lambda_(c))/(lambda_(c)^(oo))xx100`
`=(9.54)/(238)xx100=4.008%`