Question

Solution of 0.1 N NH4OH and 0.1 N NH4CI
has pH 9.25. Then pKb, of NH4OH is​

Answer 1

Answer:

NH

4

OH (a base) and NH

4

Cl (a salt) undergoes dissociation as follows:-

NH

4

OH⇌NH

4

+

+OH

−

NH

4

Cl→NH

4

+

+Cl

−

Due to the common ion effect, the reaction of dissociation of NH

4

OH shifts to the left.

Here, the given information is :-

Concentration of salt NH

4

Cl = 0.1N

Concentration of the base NH

4

OH=0.N

pH of the solution is 9.25

∴ pOH= 14 - pH = 14 - 9.25 = 4.75

We know that,

pOH=pK

b

+log

[base]

[salt]

(but here concentration of salt = concentration of base and [log

10

(1)=0])

∴pOH=pK

b

=4.75

Hence, the correct answer is option (B).