In 2-3 sentences, describe how propanoic acid (C2H5COOH) and propanoate anion (C2H5COO-) can be used to make a buffer solution if the Ka of propanoic acid is 1.34 x 10-5.
Here is what you need to know. Use this information to make your sentences.
The Henderson-Hasselbalch equation is
pH = pKa + log (base)/(acid)
Knowing what pH you want and the pKa of the acid, calculate (base) and (acid) you need to prepare the pH you want. base is propanoate. acid is propanoic acid.
To create a buffer solution using propanoic acid and propanoate anion, the ratio of their concentrations should be close to 1:1. When propanoic acid partially dissociates in water, it releases propanoate anions, and by adjusting the concentration of each component, it is possible to maintain a stable pH due to the equilibrium reaction. The Ka value of propanoic acid allows for the calculation of the necessary concentrations to maintain the desired pH range in the buffer solution.
Step 1: Calculate the pKa of propanoic acid. Since Ka = 1.34 x 10-5, pKa = -log(Ka) = -log(1.34 x 10-5).
Step 2: Determine the desired pH range for the buffer. The buffer solution works best within one pH unit of the pKa.
Step 3: Using the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), where [A-] is the concentration of propanoate anion and [HA] is the concentration of propanoic acid, solve for the ratio [A-]/[HA] that corresponds to the desired pH range.
Step 4: Prepare a solution with the determined ratio of propanoic acid and propanoate anion. For example, if the calculated ratio is 1:10, mix 1 mole of propanoic acid with 10 moles of propanoate anion to form the buffer solution.