The base-dissociation constant of ethylamine (c2h5nh2) is 6.4 at 25.0 ? ? c. the [h ] in a 1.2 10-2 m solution of ethylamine is m.

Answer is: concentration of hydrogen ions are 4·10⁻¹¹ M.
Chemical reaction: C₂H₅NH₂ + H₂O ⇄ C₂H₅NH₃⁺ + OH⁻.
Kb(C₂H₅NH₂) = 6,4·10⁻⁴.
c(C₂H₅NH₂) = 1,2·10⁻² M = 0,012 M.
[C₂H₅NH₃⁺] = [OH⁻] = x.
[C₂H₅NH₂] = 0,012 M - x.
Kb = [C₂H₅NH₃⁺] · [OH⁻] / [C₂H₅NH₂].
6,4·10⁻⁴ = x² / (0,012 M - x).
Solve quadratic equation: x = [OH⁻] = 0,0025 M.
[OH⁻] · [H⁺] = 10⁻¹⁴.
[H⁺] = 10⁻¹⁴ ÷ 0,0025 M = 4·10⁻¹¹ M.

What does that mean you dum bum