Calculate the pH of a solution prepared by dissolving 0.250 mol of benzoic acid (C₇H₅O₂H)and 0.150 mol of sodium benzoate (NaC₇H₅O₂)in water sufficient to yield 1.00 L of solution. The K_a of benzoic acid is 6.50 × 10^-5. A)4.409 B)3.965 C)10.035 D)9.591 E)5.190

Question

Quizplus · Accepted Answer

We can use the Henderson-Hasselbalch equation to solve this problem:

pH = pKa + log([A-]/[HA])

where pKa is the dissociation constant of benzoic acid, A- is the concentration of benzoate ions, and HA is the concentration of benzoic acid.

First, we need to calculate the concentrations of A- and HA in the solution.

[A-] = 0.150 mol / 1.00 L = 0.150 M

[HA] = 0.250 mol / 1.00 L = 0.250 M

Next, we need to calculate the pKa of benzoic acid.

pKa = -log(Ka) = -log(6.50 × 10-5) = 4.19

Now we can plug in the values into the Henderson-Hasselbalch equation:

pH = 4.19 + log(0.150 / 0.250) = 3.965

Therefore, the pH of the solution is 3.965. The best choice is B.

Calculate the PH of a Solution Prepared by Dissolving 0