Question
What is the pH of a 100g/l solution of potassium cyanide?
Answers
DrBob222
KCN is a salt and the pH is determined by the hydrolysis of KCN.
(KCN) = mols/L. mols = 100 g/molar mass = estimated 1.5 and 1.5 mols/L = estimated 1.5M.
............CN^- + H2O ==> HCN + OH^-
I...........1.5.............0.....0
C............-x.............x.....x
E..........1.5-x............x.....x
Kb for CN^- = (Kw/Ka for HCN) = (x)(x)/(1.5-x).
Solve for x = OH^- and convert to pH.
(KCN) = mols/L. mols = 100 g/molar mass = estimated 1.5 and 1.5 mols/L = estimated 1.5M.
............CN^- + H2O ==> HCN + OH^-
I...........1.5.............0.....0
C............-x.............x.....x
E..........1.5-x............x.....x
Kb for CN^- = (Kw/Ka for HCN) = (x)(x)/(1.5-x).
Solve for x = OH^- and convert to pH.