What is the pH of a buffer made from 0.11 M hydrocyanic acid and 0.20 M sodium cyanate? Use the Ka value from a table and the Ka expression for the acid "reacting".
I have tried to do this problem, but I still got it wrong:
(4.9e-10) * (.20/.11) = 8.91e-10
pH= -log(8.91e-10) = 9.05
If anyone can help or let me know what mistake I have made, your response will greatly be appreciated.
2007-02-24 06:37:01 · 2 answers · asked by ash 1 in Science & Mathematics ➔ Chemistry
Look up the "Henderson-Hasselback" equation. It was designed for use with buffers.
2007-02-24 06:44:23 · answer #1 · answered by spencermurraygaunt 2 · 0⤊ 0⤋
I'm assuming you mean sodium cyanide, NaCN, and not sodium cyanate, NaOCN. Cyanate would go with cyanic acid, HOCN; cyanide goes with hydrocyanic acid, HCN.
You have to use the Henderson-Hasselbach equation.
pH = pKa + log [A-]/[HA] = 9.39 + log (0.20/0.11) = 9.39 + 0.26 = 9.65
2007-02-24 14:49:14 · answer #2 · answered by TheOnlyBeldin 7 · 0⤊ 0⤋