Calculate the pH of a buffer solution prepared by dissolving 0.25 mol benzoic acid (C6H5COOH) and 0.15 mol sodium benzoate (C6H5COONa) in 1.00 L of solution. (Ka = 6.3 x 10-5)Question 8Select one:a.4.41b.2.39c.3.98d.10.03
Question
Calculate the pH of a buffer solution prepared by dissolving 0.25 mol benzoic acid (C6H5COOH) and 0.15 mol sodium benzoate (C6H5COONa) in 1.00 L of solution. (Ka = 6.3 x 10-5)Question 8Select one:a.4.41b.2.39c.3.98d.10.03
Solution
To calculate the pH of a buffer solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
where:
- pKa is the negative log of the Ka value,
- [A-] is the concentration of the base (sodium benzoate in this case), and
- [HA] is the concentration of the acid (benzoic acid in this case).
First, calculate the pKa from the given Ka:
pKa = -log(Ka) = -log(6.3 x 10^-5) = 4.20
Next, calculate the concentrations of the acid and base. Since the amounts of acid and base and the volume of the solution are given, we can calculate the concentrations as follows:
[HA] = moles of acid/volume of solution = 0.25 mol/1.00 L = 0.25 M [A-] = moles of base/volume of solution = 0.15 mol/1.00 L = 0.15 M
Now, substitute these values into the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA]) = 4.20 + log(0.15/0.25) = 4.20 - 0.22 = 3.98
So, the pH of the buffer solution is 3.98. The correct answer is c. 3.98.
Similar Questions
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