Calculate the pH of a solution that results from mixing 12 mL of 0.11 M HClO(aq) with 26 mL of 0.1 M NaClO(aq). The Ka value for HClO is 3 x 10-8.

Question

Calculate the pH of a solution that results from mixing 12 mL of 0.11 M HClO(aq) with 26 mL of 0.1 M NaClO(aq). The K_a value for HClO is 3 x 10^-8.

I used the same method I used for a similar question and got the wrong answer.

The answer is 7.82

please explain your steps, thank you :)

Answer 1

Henderson Hasselbalch equation:

pH = pKa + log [salt]/[acid]

(1). Find the pKa: pKa = -log Ka = -log 3x10^-8 = 7.523

(2). Find [salt]: (26 ml)(0.1 M) = (38 ml)(x M) and x = 0.0684 M (38 ml is the final volume after mixing 12ml + 26 ml).

(3). Find [acid]: (12 ml)(0.11 M) = (38 ml)(x M) ane x = 0.0347 M

(4). Plug values into the HH equation:

pH = 7.523 + log [0.0684]/[0.0347] = 7.523 + log 1.971 = 7.523 + 0.295

pH = 7.818 = 7.82