Determine the PH?
determine the PH solution contains 1.0M of HCN ka=6.2*10^-10 and HNO2 kb=4*10^-4?
- hcbiochemLv 72 months agoFavourite answer
What you have written as "Kb = 4X10^-4" is actually the Ka for HNO2. Because this acid is 6 orders of magnitude stronger than HCN, any contribution of HCN to the pH of this solution is insignificant and can be ignored.
HNO2 <--> H+ + NO2-
Ka = [H+][NO2-]/[HNO2] = 4X10^-4
Let [H+] = [NO2-] = x and [HNO2] = 1.0 - x. Because Ka is small, initially assume that x will be small compared to 1.0 and can be ignored. Then,
Ka = x^2 / 1.0 = 4X10^-4
x = [H+] = 0.02 M
pH = 1.7