PREPARATION AND TESTING OF BUFFER SOLUTIONS
Name: __________________________
Partner: _________________________
Date: _______________
Section/Instructor: _________________
Purpose (50 words or less):
Calculations:
1. Show the calculation of Ka for your unknown acid from the measured pH of the first
buffer (Part A).
2. Answer the following questions, (a) to (g). Note: do not forget to include dilution in these
calculations (you added 0.10 mL of acid or base to 10.00 mL of each of the test
solutions; so total final volume was 10.10 mL)
(a) Calculate the buffer capacity of pure water upon addition of HCl.
(b) Calculate the buffer capacity of pure water upon addition of NaOH.
(d) Calculate the buffer capacity of the full-strength buffer upon addition of HCl.
(e) Calculate the buffer capacity of the full-strength buffer upon addition of NaOH.
(f) Calculate the buffer capacity of the 1/10 strength buffer upon addition of HCl.
(g) Calculate the buffer capacity of the 1/10 strength buffer upon addition of NaOH.
3. (a) Show the calculation of the ratio of base to acid required for your assigned pH.
(b) Calculate the percentage error between the assigned pH and the measured pH of
the second buffer you prepared.
On attached page(s) provide answers to the following questions (respond with
clarity in concise well-structured sentences):
1. What is the buffer range expected for your buffers (both the “full strength” and the
diluted)? Is the buffer range the same for both, different, . . . ? Explain your response . .
. back it up with theory and with experimental data.
2. Discuss the buffer capacity of each buffer (“full strength” and diluted). Is the buffer
capacity the same for both buffers? If not which is larger? Explain your response . . .
back your answer up with experimental data. Why might it be the expected result?
3. Of what components does a buffer consist?
a. Which buffer component neutralizes added HCl? Write the neutralization reaction.
b. What buffer component neutralizes added NaOH? Write the neutralization reaction.
4. Examine the reactions you wrote in response to 3a and 3b above. Discuss the following:
a. When HCl is neutralized what (aside from water) is created?
b. When NaOH is neutralized what (aside from water) is created?
5. Consider a hypothetical buffer made from a weak acid, HA, (Ka = 1.0 x 10-4) and its
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conjugate base, A , (assume there is no change in volume in parts “b” and “c”):
a. If the [HA] = [A-] = 0.10 M, what is the pH of the buffer?
b. If 0.010 mole of HCl (g) is added to 1.00 L of this buffer, what is the new pH?
c. If 0.010 mole of NaOH (s) is added to 1.00 L of this buffer, what is the new pH?