You need to produce a buffer with pH of 5.75. You have a solution with 0.5M of acid (X) (pKa=4.75). What is the concentration of base must you add to achieve the desired pH?
To produce a buffer with a pH of 5.75, you need to add a base to your acid solution in order to create a conjugate acid/base pair.
First, determine the ratio of the concentration of acid to its conjugate base needed to achieve a buffer with the desired pH. This can be done using the Henderson-Hasselbalch equation:
pH = pKa + log([base]/[acid])
Substituting the given values:
5.75 = 4.75 + log([base]/[acid])
Rearranging the equation, we have:
log([base]/[acid]) = 5.75 - 4.75
log([base]/[acid]) = 1
To remove the logarithm, we can rewrite the equation:
[base]/[acid] = 10^1
[base]/[acid] = 10
Since the concentration of the acid (X) in the solution is given as 0.5M, we can let [acid] = 0.5M. By substituting this value into the equation:
[base]/0.5 = 10
Now solve for [base]:
[base] = 10 * 0.5
[base] = 5M
Therefore, you need to add a base with a concentration of 5M to your acid solution to achieve a buffer with a pH of 5.75.