Assignment: Chemistry of Life- pH and Buffers
Activity 1
1. Calculate the volume of 1 M NaOH needed to prepare 10.0 mL of a 0.10 M solution.
2. Calculate the volume of 1 M HCl needed to prepare 10.0 mL of a 0.10 M solution.
Data Table 1
|
|
Initial pH
|
pH after 1 drop 0.1M HCl
|
pH after 10 drops 0.1M HCl
|
pH after 1 drop 0.1M NaOH
|
pH after 10 drops 0.1M NaOH
|
|
Water
|
|
|
|
|
|
|
pH 4 buffer
|
|
|
|
|
|
|
pH 6 buffer
|
|
|
|
|
|
|
pH 8 buffer
|
|
|
|
|
|
3. In Activity 1, what happened to the pH of the water sample as 0.1 M HCl was added? How did this compare to what happened with addition of one drop of 0.1 M HCl to each buffer solution?
4. In Activity 1, why did the pH of the buffer solutions change after the addition of 10 drops of 0.1 M NaOH? Activity 2
Activity 2
Data Table 2
|
|
Initial pH
|
pH after 1 drop 0.1M NaOH
|
pH after 2 drops 0.1M NaOH
|
pH after 4 drops 0.1M NaOH
|
pH after 8 drops 0.1M NaOH
|
|
100%
|
|
|
|
|
|
|
50%
|
|
|
|
|
|
|
25%
|
|
|
|
|
|
|
12.5%
|
|
|
|
|
|
5. In Activity 2, which concentration was the effective buffer? Explain what happened chemically as the buffer became more dilute.
6. Explain how the buffer could be diluted (in Activity 2), yet maintain the same pH.Hint: Reference the Henderson-Hasselbalch equation.
Photos
Photo 1
Insert photo of results of Activity 1.
The following should be visible in this photo:
• Row and column labels
Photo 2
Insert photo of results of Activity 2.
The following should be visible in this photo:
• Row and column labels.