Complete Question
The pKb values for the dibasic base B are pKb1=2.10 and pKb2=7.54. Calculate the pH at each of the points in the titration of 50.0 mL of a 0.60 M B(aq) solution with 0.60 M HCl(aq).
(a) before addition of any HCl (b) after addition of 25.0 mL of HCl
Answer:
a The value is
b
Explanation:
From the question we are told that
The first pKb value for B is
The second pKb value for B is
The volume is
The concentration of B is
The concentration of
Generally the reaction equation showing the first dissociation of B is
Here the ionic constant for B is mathematically represented as
Let denot the concentration of [BH^+] as z and since then is also z
So [B] = 0.60 - z
Here is ionic constant for the first reaction of a dibasic base B and the value is
So
=>
using quadratic formula to solve this equation
Hence the concentration of is
Generally
=>
=>
Generally the pH is mathematically represented as
Generally the volume of at the second dissociation of the base B is
The volume of the half way to the first dissociation of the base is 25mL
Now the pOH at half way to the first dissociation of the base is
=>
=>
Generally the pH after addition of 25.0 mL of HCl is
\
=>