What concentrations of acetic acid (pKa = 4.76) and acetate would be required to

Question

What concentrations of acetic acid (pKa = 4.76) and acetate would be required to prepare a 0.15 M buffer solution at pH 5.0?

What concentrations of acetic acid (pKa 4.76) and acetate would be required to prepare a 0.15 M buffer solution at pH 5.0? Note that the concentration and/or pH value may differ from that in the first question. STRATEGY 1. Rearrange the Henderson equation to solve for the ratio of base (acetate) to acid (acetic acid), CA VIHA 2. Use the mole fraction of acetate to calculate the concentration of acetate. 3. Calculate the concentration of acetic acid. That is, there are 1.7 molecules Step 1: The ratio of base to acid is 1.7. of acetate for each molecule of acetic acid. Step 2: The mole fraction of acetate is 0.63, and the concentration of acetate is 0.094. Step 3: Calculate the concentration of acetic acid. Number acetic acid O

Explanation / Answer

use:
pH = pKa + log {[acetate]/[acetic acid]}
5.0 = 4.76 + log (0.63/[acetic acid])
0.24 = log (0.63/[acetic acid])
0.63/[acetic acid] = 1.738
[acetic acid] = 0.36 M

Answer: 0.36 M

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