What am I doing wrong in this titration problem?
Calculate the ph at the equivalence point for thefollowing titration 0.20M HCl versus 0.20M methylamine (CH3NH2).The Ka of methylammonium is 2.3x10^-11.
First I have to divide .20M methylamine by 2(Why?) to get .10M
Then, I set up the equilibrium:
(2.3 x 10^-11) = x^2 / .10M
Since the ka is SO small, I just multiplied .10 with (2.3 x10^-11) to get 2.3x10^-12, which is wrong.
Why is this wrong? Since the Ka is small, the approxiamationmethod should work and I won't need to do the quadratic. Instead, Iam told that the x value is 1.5x10^-6 from the quadratic.
