What is the pH of a buffer solution that is 0.15 M propionic acid and 0.20M sodium propionate?
How do I start this problem
Use the Henderson-Hasselbalch equation.
pH = pKa + log[(base)/(acid)]
Show your work if you get stuck.
well the only problem im having is finding the pKa
My quant book lists 1.34 x 10^-5 for Ka. And Wikipedia lists a pKa of 4.88 which is almost the same, but not quite. Take your pick.
i think i will choose the 4.88 thank you
To find the pH of a buffer solution, you need to use the Henderson-Hasselbalch equation, which is expressed as:
pH = pKa + log ([A-]/[HA])
Here's how you can go about solving this problem:
1. Find the pKa value of propionic acid (HA). The pKa value can be obtained from a reference source like a chemistry textbook or a database. Let's assume the pKa value of propionic acid is 4.87.
2. Calculate the ratio of the concentration of the conjugate base (A-) to the concentration of the acid (HA). In this case, the concentration of propionic acid (HA) is given as 0.15 M, and the concentration of sodium propionate (A-) is given as 0.20 M. Therefore, the ratio [A-]/[HA] would be (0.20 M)/(0.15 M) = 1.33.
3. plug the pKa value and the ratio [A-]/[HA] into the Henderson-Hasselbalch equation:
pH = 4.87 + log (1.33)
4. Use a calculator to find the logarithm of the ratio and add it to the pKa value to calculate the pH.
For example, the log (1.33) is approximately 0.123, so the pH would be:
pH = 4.87 + 0.123 = 5.00 (rounded to two decimal places)
Therefore, the pH of the buffer solution that is 0.15 M propionic acid and 0.20 M sodium propionate is approximately 5.00.