Activity: Buffer Solutions
We know that a buffer is defined as a solution that can resist a change in pH, even
when small amounts of strong acid or base is added to it. We also know that a buffer
solution must contain approximately equal amounts of a conjugate acid-base pair.
Let’s test this out!
PROCEDURE:
First we need to create the buffer. We will do this by adding a small amount of strong
acid (HCl(aq)) to a weak base (sodium acetate).
1. Measure 20.0mL of sodium acetate in a graduated cylinder and then transfer the
sodium acetate solution into a 50mL beaker.
2. Using a graduated pipette, measure out 2.0mL of HCl(aq) and add this to the
20.0mL of sodium acetate in the 50mL beaker. We should now have a buffer
solution.
Now let’s test our buffer compared to water.
3. Using a graduate cylinder, measure out 10mL of buffer solution and transfer it to
a 50 mL beaker.
4. Add several drops of universal indicator to the sample.
5. Using a disposable pipette, count how many drops of NaOH(aq) can be added to
the buffer solution until a significant color change is observed?
Drops of NaOH(aq) added to buffer:______________
6. Rinse solution down the drain and rinse 50mL beaker with water.
7. Repeat steps 3-6 but with water instead of a buffer solution and compare how
many drops of NaOH(aq) can be added to water before a significant color change
is observed.
Drops of NaOH(aq) added to water:______________
8. Using a graduate cylinder, measure out a new 10mL of buffer solution and
transfer into a 50mL beaker.
9. Add several drops of thymol blue indicator to the sample.
10. Using a disposable pipette, count how many drops of HCl(aq) can be added to the
buffer solution until a significant color change is observed.
Drops of HCl(aq) added to buffer:______________
11. Rinse solution down the drain and rinse 50mL beaker with water.
12. Repeat steps 8-11 but with water instead of a buffer solution and compare how
many drops of HCl(aq) can be added to water before a significant color change is
observed.
Drops of HCl(aq) added to water:______________