The [H] in a 1.6×10^2 M solution of ethylamine is ____?
The answer is supposed to be 3.5 x 10^12, but somehow I keep getting 3.1×10^12. So, if you can show your work that would be a huge help!
1 Answer

C2H5NH2 + H2O <=> C2H5NH3+ + OH
start
1.6 x 10^2
change
x . .. . . . . . . . . . . . .. . .+x .. . . . .+x
at equilibrium
1.6 x 10^2x. . . . .. . . . . .x. . . .. . . x
6.4 x 10^4 = x^2 / 1.6 x 10^2x
we must solve by quadratic formula because x is not negligible compared to 1.6 x 10^2
1.0 x 10^5 – 6.4 x 10^4 x = x^2
x^2 + 6.4 x 10^4 – 1.0 x 10^5 =0
x = – 6.4 x 10^4 + sq.rt ( 4.1 x 10^7 + 4.0 x 10^5)/2 = 0.0028 M = [OH]
[H+]= Kw/[OH]= 1.0 x 10^14/ 0.0028 = 3.5 x 10^12 M