At 298 K, the molar conductivities at infinite dilution `(^^_(m)^(@))` of `NH_(4)CI, KOH` and KCl are 152.8, 272.6 and `149.8 S cm^(2) mol^(-1)` respectively. The `^^_(m)^(@)` of `NH_(4)OH` in `Scm^(2)mol^(-1)` and % dissociation of `0.01 M NH_(4)OH` with `^^m = 25.1 S cm^(2) mol^(-1)` at the same temperature are

Options

A. 275.6, 0.91
B. 275.6, 9.1
C. 266.6, 9.6
D. 30, 84

Answer

B

Explanation

`(^^)_(m)^(@) NH_(4)OH= (^^)_(m)^(@)(NH_(4)Cl+ KOH)- (^^)_(m)^(@)(KCl)`
`= 152.8+ 272.6- 149.8= 275.6 S cm^(2) "mol"^(-1)`
Degree of dissociation (a)= `((^^)_(m))/((^^)_(m)^(@))= (25.1)/(275.6)= 0.091`
`:.` % degree of dissociation= 9.1%