Final answer:
To calculate percent ionization of benzoic acid in the presence of sodium benzoate, use the Henderson-Hasselbalch equation for pH and then find [H3O+]. Finally, use the [H3O+] and the initial benzoic acid concentration to determine percent ionization.
Step-by-step explanation:
To calculate the percent ionization of 0.18 M benzoic acid in a solution containing 0.10 M sodium benzoate, we can use the Henderson-Hasselbalch equation to find the pH of the solution, since we have a mixture of a weak acid and its conjugate base. The equation is given by pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base (sodium benzoate) and [HA] is the concentration of the weak acid (benzoic acid).
The pKa for benzoic acid is approximately 4.2.
First, calculate the pH:
pH = 4.2 + log(0.10/0.18)
Once we have the pH, we can calculate the [H3O+] concentration using the formula [H3O+] = 10-pH.
Next, calculate the percent ionization:
Percent ionization = ([H3O+]/[HA]) * 100%
After computing [H3O+] from the pH, plug this value and the initial concentration of benzoic acid into the percent ionization formula to get the final result.