Consider a 0.80M solution of HCN. The Ka of HCN is 6.2x10-10. What are the major species in solution? Calculate the pH of this solution.

Answer 1

..........HCN ==> H^+ + CN^-
initial...0.80M...0......0
change.....-x......x.....x
equil....0.80-x....x.....x

Ka = (H^+)(CN^-)/(HCN)
Substitute and solve for x and convert to pH.
After you finish the calculation you will know what the major species are. Don't forget H2O as a major component.