Equilibrium Question 750

Question: When 10 ml of 0.1 M acetic acid ( $ pK_{a} $ . = 5.0) is titrated against 10ml of 0.l Mammonia solution ( $ pK_{b} $ =5.0), the equivalence point occurs at pH

Options:

A) 5.0

B) 6.0

C) 7.0

D) 9.0

Show Answer

Answer:

Correct Answer: C

Solution:

$ pK_{a}=-\log K_{a}p{K_{a,}}pK_{b}=-\log K_{b} $

$ pH=-\frac{1}{2}[logK_{a}+logK_{w}-logK_{b}] $

$ =-\frac{1}{2}[-5+log(1\times {10^{-14}})-(-5)] $

$ =-\frac{1}{2}[-5-14+5]=-\frac{1}{2}(-14)=7 $



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