Chemistry of Life

2

 

Chemistry of Life: pH and Buffers Student Name Date

Data

 

Activity 1

 

Calculate the volume of 1 M NaOH needed to prepare 10.0 mL of a 0.10 M solution.

 

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

 

 

 

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?

 

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%

 

 

In Activity 2, which concentration was the effective buffer? Explain what happened chemically as the buffer became more dilute.

 

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

 

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