Example 1. Calculate the molar ratio [salt]/[acid] required to prepare an acetate buffer solution with
pH = 5.2.
Answer 1. Acetate buffer is composed from acetic acid (pKa=4.76) and its salt (e.g. sodium acetate). To make the calculation we use the buffer equation for acid- conjugate base pair. Accordingly, the solution to the above example is as the following:
Example 2. What is the pH at which [salt] = [acid] for an acetate buffer solution.
Answer 2. Given that [salt] = [acid] then [salt]/ [acid] = 1. The following describes the answer:
Example 3. Calculate the pH for a buffer solution composed from 0.01 M acetic acid (pKa = 4.76) and 0.02 M sodium acetate.
Answer 3. Using the buffer equation the answer is:
Example 4. Assume that an acetate buffer with a pH = 5.4 is needed such that the total buffer concentration ([salt] + [acid]) is equal to 0.05 M. Calculate the molar concentration for both acetic acid ([acid]) and sodium acetate ([salt]) required to make such a solution.
Answer 4. This example is solved in two steps. The first step involves finding the ratio [salt]/ [acid]. The second step involves solving two equations to find the required concentrations. The following describes the answer:
Step 1.
pH = 5.2.
Answer 1. Acetate buffer is composed from acetic acid (pKa=4.76) and its salt (e.g. sodium acetate). To make the calculation we use the buffer equation for acid- conjugate base pair. Accordingly, the solution to the above example is as the following:
Example 2. What is the pH at which [salt] = [acid] for an acetate buffer solution.
Answer 2. Given that [salt] = [acid] then [salt]/ [acid] = 1. The following describes the answer:
Example 3. Calculate the pH for a buffer solution composed from 0.01 M acetic acid (pKa = 4.76) and 0.02 M sodium acetate.
Answer 3. Using the buffer equation the answer is:
Example 4. Assume that an acetate buffer with a pH = 5.4 is needed such that the total buffer concentration ([salt] + [acid]) is equal to 0.05 M. Calculate the molar concentration for both acetic acid ([acid]) and sodium acetate ([salt]) required to make such a solution.
Answer 4. This example is solved in two steps. The first step involves finding the ratio [salt]/ [acid]. The second step involves solving two equations to find the required concentrations. The following describes the answer:
Step 1.
Step 2.
Example 5. What is the pH of a solution containing 0.09 M ephedrine (pKb = 4.64) and 0.01 M ephedrine hydrochloride (salt of ephedrine) given that pKw = 14.
Answer 5. To make the calculation we use the buffer equation for base- conjugate acid pair. Accordingly, the solution to the above example is as the following:
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