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Chemistry LibreTexts

Buffers Solutions

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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

1. Calculate the pH of a buffer solution made from equal amounts of 0.30 M hydrofluoric acid and 0.70 M sodium fluoride.  Ka = 7.1 x 10-4 [H+] = 3.04 x 10-4; pH = 3.52

2. Calculate the pH of a buffer solution made from 0.30 M hydrofluoric acid and 0.70 M sodium fluoride after the addition of 0.08 mol of NaOH to 1 L of this solution.  Assume no change in volume. Ka = 7.1 x 10-4    [H+] = 2.00 x 10-4; pH = 3.70

3. Calculate the pH of a 0.08 M NaOH solution.  Compare to the pH found in problem 2.
pOH = 1.10; pH = 12.90

4.  What would be the buffer range for an acid if its Ka = 7.1 x 10-4 ?
pKa = 3.15; buffer range 2.15 to 4.15

5. Calculate the pH of a buffer solution made from 0.30 M hydrofluoric acid and 0.70 M sodium fluoride after the addition of 0.04 mol of HCl to 1 L of this solution.  Assume no change in volume. Ka = 7.1 x 10-4   [H+] = 3.66 x 10-4; pH = 3.44

6.  Calculate the pH of a 0.04 M HCl solution.  Compare to the pH found in problem 5.
pH = 1.40