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No indicator is suitable when titrating weak acid with weak alkali
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5
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This was a statement in my book:
A solution of a weak acid cannot be titrated with a weak base using an indicator to find the end-point because the pH change is too gradual close to the equivalence point.
Could someone please elaborate the bold text.
acid-base ph titration
shareimprove this question
asked May 31 '14 at 13:16
Eliza
86241329
2
Check this link and search for the section "Titration curves for weak acid v weak base". Be sure to click on the "indicator" link in the section's note, too. Does that help? – Nicolau Saker Neto May 31 '14 at 13:30
if there is a weak base and a weak acid, there will be at least two pKs, complicating the titration curve. The full pH range may be unobtainable by adding a weak base. – DavePhD May 31 '14 at 13:45
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1 Answer
active oldest votes
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6
down vote
An indicator works when the solution's pH is in its range. It's not necessarily the equivalence point. The point is called the end point where it actually changes color.
If the difference in volume is small between the equivalence and end points, then the indicator can be used. Since a gradual change implies more volume must be added to obtain the same pH change in other acid base titration, the difference between equivalence point and end point(if you use indicator) will be more and therefore indicator will not be suitable for it.
shareimprove this answer
edited Jul 31 '14 at 13:45
jonsca♦
1,68261947
answered May 31 '14 at 16:58
DSinghvi
1,2891628
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asked
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rev 2017.4.13.25686
Chemistry
Questions
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Users
Badges
Unanswered
Ask Question
_ Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers and students. Join them; it only takes a minute:
Sign up
Here's how it works:
Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top
No indicator is suitable when titrating weak acid with weak alkali
up vote
5
down vote
favorite
This was a statement in my book:
A solution of a weak acid cannot be titrated with a weak base using an indicator to find the end-point because the pH change is too gradual close to the equivalence point.
Could someone please elaborate the bold text.
acid-base ph titration
shareimprove this question
asked May 31 '14 at 13:16
Eliza
86241329
2
Check this link and search for the section "Titration curves for weak acid v weak base". Be sure to click on the "indicator" link in the section's note, too. Does that help? – Nicolau Saker Neto May 31 '14 at 13:30
if there is a weak base and a weak acid, there will be at least two pKs, complicating the titration curve. The full pH range may be unobtainable by adding a weak base. – DavePhD May 31 '14 at 13:45
add a comment
1 Answer
active oldest votes
up vote
6
down vote
An indicator works when the solution's pH is in its range. It's not necessarily the equivalence point. The point is called the end point where it actually changes color.
If the difference in volume is small between the equivalence and end points, then the indicator can be used. Since a gradual change implies more volume must be added to obtain the same pH change in other acid base titration, the difference between equivalence point and end point(if you use indicator) will be more and therefore indicator will not be suitable for it.
shareimprove this answer
edited Jul 31 '14 at 13:45
jonsca♦
1,68261947
answered May 31 '14 at 16:58
DSinghvi
1,2891628
add a comment
Your Answer
Sign up or log in
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Name
By posting your answer, you agree to the privacy policy and terms of service.
Not the answer you're looking for? Browse other questions tagged acid-base ph titration or ask your own question.
asked
2 years, 10 months ago
viewed
9588 times
active
10 days ago
UPCOMING EVENTS
Spring cleaning
April 2017
NIST CompChem Comparison & Benchmark Database
9 votes · comment · stats
Related
1
Finding the Ka of a weak acid after addition of a strong base
2
What's happening at the beginning of a weak acid titration?
3
Weak base titrated with a strong acid
5
Calculating pH for titration of weak base with strong acid
1
How to calculate the sufficient ratio of acid and corresponding base of the indicator that allows to clearly observe the endpoint of a titration?
5
Shape of Weak-Strong Acid-Base Titration
1
Phenolphthalein as a indicator for the titration of benzoic acid
5
Is this problem about acid-base titration wrong?
0
Weak acid weak base titration
0
Acid-Base Titration, why does for a weak acid indicator, [HA] = [A-]
Hot Network Questions
Möbius Inversion and Fourier transform.
ls option to list files without reference to extension?
Detect Sound From Google Chromecast Audio
Typesetting linguistic rewrite rule
Check if a number N is a power of K
more hot questions
question feed
about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback
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Stack Overflow
Server Fault
Super User
Web Applications
Ask Ubuntu
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Software Engineering
Unix & Linux
Ask Different (Apple)
WordPress Development
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Information Security
Database Administrators
Drupal Answers
SharePoint
User Experience
Mathematica
Salesforce
ExpressionEngine® Answers
Cryptography
Code Review
Magento
Signal Processing
Raspberry Pi
Programming Puzzles & Code Golf
more (7)
Photography
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Movies & TV
Music: Practice & Theory
Seasoned Advice (cooking)
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Travel
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more (17)
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site design / logo © 2017 Stack Exchange Inc; user contributions licensed under cc by-sa 3.0 with attribution required
rev 2017.4.13.25686
