simple chemistry A2 level MCQ

Ammonia (NH3), butylamine (CH3CH2CH2CH2NH2) and phenylamine (C6H5NH2) all
form alkaline solutions in water. The order of increasing pH of equimolar solutions

hello you guys probably have often seen this sort of question. How do we know which one forms more acidic solution and which one forms more basic solution? Do we just need to momorise?

You can commit it to memory if you like, but I think it's better to understand it so you don't have to.

It's all about the avaliability of the lone pair on the nitrogen - if electron density is being pushed onto it (like for an example by an alkly group via inductive effect) then it becomes more avaliable and therefore more basic (easier to grab protons).

Alternatively, If you have the nitrogen next to an aromatic ring, this will pull the lone pair into it - this mean's it's less avaliable and therefore less basic