Posted by Robert on .
Calculate the pH of .100M of HClO2.
HClO2 is a weak acid.
HClO2 + H2O ==> H3O^+ + ClO2^-
Ka = (H3O^+)(ClO2^-)/(HClO2)
Set up an ICE chart, calculate (H^+) and convert that to pH.
I keep getting 1.479, but the program I use for homework keeps counting it wrong. Am I totally off?
I don't know what value you used for Ka for HClO2. I looked on the net and found 0.012 in two places.
It would have been better if you showed your work, then I could find the trouble. I suspect you didn't solve the queadratic but I could be mistaken.
The equation should be
Ka = (x)(x)/(0.1-x) = 0.012 or whatever you used for Ka. Using my value for Ka, I found H^+ = 0.02916 which gives a pH of 1.53 something. To get 1.479 you must have a H^+ of 0.03319. But I can't compare our answers since we may have used totally different values for Ka. If that isn't the problem with your answer then the next best guess is that you are keying in too many or too few significant figures. That is often the problem with the data base answers.