Answer and Explanation
The isomer picked is the N-Propylamine.
It has a lone pair of electron available on the electron rich Nitrogen and no formal charge.
Since it will be hard to draw the Lewis structure in this answer format, I'll attach a picture of the Lewis structure to this answer.
The lone pair of electron is shown by the two dots on the Nitrogen atom.
As we know, NaOH is a strong Base and completely dissociates in water as given below,
NaOH + H₂O → Na⁺ ₍aq₎ + OH⁻ ₍aq₎
So, the concentration of OH⁻ Ions will be the same as that the concentration of NaOH i.e. 0.018 M.
So,
[OH⁻] = 0.018 M
Basic unit of a chemical element or atoms as a source of nuclear energy
straight out of dictionary