1) A 15.1 mL sample of a 0.446 M aqueous hypochlorous acid solution is titrated
ID: 955172 • Letter: 1
Question
1) A 15.1 mL sample of a 0.446 M aqueous hypochlorous acid solution is titrated with a 0.397 M aqueous potassium hydroxide solution. What is the pH at the start of the titration, before any potassium hydroxide has been added?
pH =
2) What is the pH at the equivalence point in the titration of a 22.5 mL sample of a 0.304 M aqueous hydrocyanic acid solution with a 0.327 M aqueous potassium hydroxide solution?
pH =
3) A 43.3 mL sample of a 0.477 M aqueous hydrofluoric acid solution is titrated with a 0.476 M aqueous barium hydroxide solution. What is the pH after 12.0 mL of base have been added?
pH =
Explanation / Answer
1)
HClO + KOH = H2O + KClO
initially
HClO = H+ and ClO-
Ka = [H+][ClO-]/[HClO]
Ka = 3.5*10^-8
then
[H+]= [ClO-]= x
[HClO] = 0.446-x
substitute
(3.5*10^-8) = (x*x/(0.446-x)
x = 1.24*10^-4
[H+] = 1.24*10^-4
pH = -log(1.24*10^-4) = 3.906
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