A 40 ml solution of weak base BOH is titrated with 0.1 (N) HCl. The pH of solution is found to be 10.04 and 9.14 after the addition of 5 ml of 20 ml of acid respectively. Detemine pK b of weak base in nearest possible integers Given : log 2 = 0.3 and log 3 = 0.48
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
5
Sol. Let initially we have a moles of weak base BOH
BOH + HCl ⎯→ BCl + H 2 O
A 5 × 10 –4 moles
(a – 5 × 10 –4 ) — 5 × 10 –4 moles
After addition of HCl, the resulting solution act as basic buffer.
∴ pOH = 3.96
= pK b + log 
….(i)
BOH + HCl ⎯→ BCl + H 2 O
A 20 × 10 –4 (a – 20 × 10
–4 ) — (20 × 10 –4 )
4.86 = pK b + log 
----------(ii)
(ii) —(i)
0.9 = log 
× 
= log 
= log 8
or 
= 8
or a – 5 × 10 –4 = 2 (a – 20 × 10 – 4 )
or a = 35 × 10 –4 ∴ 4.86 = pK b + log 
or 4.86 = pK b + log 
or 4.86 = pK b + 0.6 – 0.48
or pK b = 4.74 ~ 5
Prepare Smarter with CGP Edu
Get practice questions, solutions, and test series in one place.
Write a Review
Share your experience with this question and solution.
Commentary
Send your comment, doubt, correction, or feedback to admin.
Similar Questions
Explore conceptually related problems