Explain how pH changes can be minimised using a mixture of a weak acid and it's conjugate base

MYTUTOR SUBJECT ANSWERS

Answers / Chemistry / A Level / Explain how pH changes can be minimised using a mixture of a weak acid and it's conjugate base

353 views

Explain how pH changes can be minimised using a mixture of a weak acid and it's conjugate base

This mixture of a weak acid (HA) and it's conjugate base (A^-) acts as a buffer. A buffer is a solution with a highly stable pH. On addition of small amounts of either a strong acid or a strong base, this buffer will resist changes in pH.

Before addition:
The acid and it's conjugate base may react with each other, but this will result in no net change as both acid and base are reformed in the reaction.

HA + A^---> A^-+ HA

Both the acid and it's conjugate base are weak so rarely react with the water present.

As a result of both of these, the weak acid and it's conjugate base will remain in high concentration in the solution.

On addition of strong base:
As the base added is strong, it will react with the weak acid. The equation below demonstrates how the H⁺from the weak acid is donated to the ^-OH group from the base.

^-OH + HA --> A^-+ H₂O

As the ^-OH group is used up by the reaction, the pH will only change minimally.

On addition of strong acid:
The H⁺from the strong acid will react with the weak base to form the weak acid HA.

H⁺ + A^- --> HA

The additional H⁺ contributed by adding the strong acid is mopped up by the weak base. Therefore the pH will only change minimally

Cora T. A Level Chemistry tutor, GCSE Chemistry tutor

8 months ago

Answered by Cora, an A Level Chemistry tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

122 SUBJECT SPECIALISTS

Lucy S. A Level Chemistry tutor, GCSE Chemistry tutor, A Level Maths ...

View profile

£22 /hr

Lucy S.

Degree: Chemistry (Masters) - Durham University

Subjects offered:Chemistry, Maths

“Reading Chemistry at Durham University with expertise in Chemistry and Mathematics (A*A*) at GCSE/A-level”

5.0

5 reviews | 13 completed tutorials

Save profile

Michal D. A Level Chemistry tutor, IB Chemistry tutor, Mentoring Chem...

View profile

£36 /hr

Michal D.

Degree: Chemistry (Masters) - Oxford, Jesus College University

Subjects offered:Chemistry, -Personal Statements-+ 1 more

“A 3rd year Chemistry student at University of Oxford looking to help you with any problems with the subject. ”

4.9

83 reviews | 190 completed tutorials

Save profile

£26 /hr

Lorenzo C.

Degree: Biomedical Sciences with Honours in Infectious Diseases (Bachelors) - Edinburgh University

Subjects offered:Chemistry, Physics+ 1 more

“5th in the World at International A-Level Biology Over two years experience in tutoring!”

5.0

46 reviews | 89 completed tutorials

Save profile

See more A Level Chemistry tutors

About the author

View profile

Cora T.

Currently unavailable: for regular students

Degree: Chemistry (Bachelors) - Durham University

Subjects offered:Chemistry

“About Me I am a 2nd year chemistry student at Durham University. I have have always been enthusiastic about the sciences and studied a combination of them for A-level. This has helped my understanding of chemistry as I have progressed...”

MyTutor guarantee

Save profile

Version:	3.46.1
Build:	38ba4033af73
Time:	2017-06-23T10:54:26Z

MYTUTOR SUBJECT ANSWERS

Explain how pH changes can be minimised using a mixture of a weak acid and it's conjugate base

Still stuck? Get one-to-one help from a personally interviewed subject specialist

122 SUBJECT SPECIALISTS

About the author

You may also like...

Other A Level Chemistry questions

One-to-one help is at your fingertips