Consider the titration curves for the following three bases, all titrated with t
ID: 991912 • Letter: C
Question
Consider the titration curves for the following three bases, all titrated with the same HBr(aq) solution:
a) 25.0 mL of 0.10 M KOH
b) 25.0 mL of 0.10 M dimethyl amine, (CH3)2NH
c) 25.0 mL of 0.10 M methyl amine, CH3NH2
For these three titrations, answer the following questions: (Hint: You need to look up some information that can be found in your text book in order to answer most of these questions.)
i) Compare the volume of acid needed to reach the equivalence point for the three titrations.
ii) Rank the initial pH of the three base solutions, before any acid was added, from LOWEST pH to HIGHEST pH from LEFT to RIGHT.
iii) Rank the pH at the equivalence point for the three titrations from LOWEST pH to HIGHEST pH from LEFT to RIGHT.
iv) Which one of these three titration curves will exhibit the smallest overall pH change within the steep equivalence point region?
v) Which of the titration curves will exhibit a buffer region? (List all that apply.)
Explanation / Answer
I ) for all same volume of HBr is needed
II ) initial pH of KOH is highest next (CH3)2NH , CH3NH2
KOH > (CH3)2NH > CH3NH2
III) pH at equivalence point
KOH > (CH3)2NH > CH3NH2
for KOH exactly 7
(CH3)2NH and CH3NH2 , pH < 7.
here (CH3)2NH Kb value more than CH3NH2 . so it is more basic than CH3NH2
IV ) KOH
V) (CH3)2NH and CH3NH2 will have buffer regions . because two are weak bases.