Posted by Jenni on Wednesday, December 15, 2010 at 4:58pm.
...........HCN + H2O ---> H3O^+ + CN^-
initial....0.100...........0.......0
change.....-x..............+x......+x
final...0.100-x.............x.......x
Ka = (H3O^+)(CN^-)/(HCN)
Now substitute into Ka expression the values from the ICE chart.
Ka for HCN is 7.2E-4 from an old book of mine but you need to use the value found in your text/notes.
7.2E-4 = (x)(x)/(0.1-x)
Solve for x = (H3O^+) and convert to pH.
(CN^-) is the same.
NOTE: If you solve the EXACT equation I have written above you must solve a quadratic equation. Most calculators do that with no problem.
Post your work if you get stuck.
So is Ka water H2o? not sure where you got 7.20 in my chart 7.2 goes with H2PO4^-
there is nothing for (H3O+) but I got 4.69 for CN- and 9.31 for HCN
I am so lost...
If you re-read my post I told you where I obtained 7.2E-4. Since you didn't include it in your post I had to look in one of my old texts BUT I told you to look in your text and use the value you found there.
What do you mean there is nothing for H3O^+. That's what you are calculating. And HCN can't possibly be 9.31. It was 0.100 in the problem.
Related Questions
chemistry - What is the pH of a 1.24 mol/L solution of HCN(aq) if its Ka = 6.2 x...
Chemistry! - Determine the pH of the following, giving your answers to two ...
math - round result to two decimal places...the answer i have is: 7.023 so two ...
chem - Calculate the pH of 0.20 M NaCN solution. NaCN ---> Na+ + CN- CN...
general chem - A certain monoprotic weak acid with Ka = 0.49 can be used in ...
general chem - A certain monoprotic weak acid with Ka = 0.49 can be used in ...
Quantitative Chemistry - Ignoring activities, determine the molar solubility (S...
Chemistry - How does one calculate the pH of a solution that is only 1.84% ...
chemistry - a sample of 20.0 mL of 0.100 M HCN (Ka=6.2*10^-10) is titrated with ...
CHEMISTRY URGENT!!! - Determine the pH (to two decimal places) of the solution ...
For Further Reading
