Consider the following reactions: 1. HA + OH- = A- + H20 2. HA + H30+ = H2A+ + H
ID: 692781 • Letter: C
Question
Consider the following reactions:
1. HA + OH- = A- + H20
2. HA + H30+ = H2A+ + H20
3. HA + H20 = H30+ + A
4. HA + OH- = H3O+ + A
5. A- + H30+ = HA + OH-
6. A- + H20 = HA + OH-
7. A- + OH- HA + O2-
Which one of these reactions (enter only the reaction number, 1 to 7) is mainly responsbile for the fact that base aded to the buffer solutio causes only a very small change in pH?
Which one of the above reactions (enter only the reaction number, 1 to 7) is mainly responsbile for the fact that buffer solutions can also react witha small amount of strong acid, H30+, without a large change in pH?
Explanation / Answer
Buffers are solutions that resist change to pH upon addition of small amounts of either an acid or a base.
Consider the following reactions:
4. HA + OH- ----> H3O+ + A-
In the above reaction conjugate acid neutralizes added strong base thus, responsbile for the fact that base added to the buffer solution causes only a very small change in pH.
Consider the following reactions:
5. A- + H3O+ ----> HA + OH-
The pH does not change very much because (A-] I (HA] does not change very much.
As the amount of strong acid added is small as compared to the amount of conjugate base in the buffer . Therefore,the above reaction(5) is mainly responsbile for the fact that buffer solutions can also react with a small amount of strong acid, H3O+, without a large change in pH.