Question

For `HSO_4^(-)`, `NH_3(aq)`, and `NH_4^(+)` which species are Bronsted acids, and which are Bronsted bases?

Answer 1

As far as I can see (and you made me pull out my spex), I would amend `c`, `e`, and `f`.....Why?

Explanation:

`c.`, you got `"bisulfate ion"`; in aqueous solution this is a moderately strong acid. Certainly we treat `H_2SO_4` as a diacid in aqueous solution.

`e.`, you got `"ammonium ion"`; in aqueous solution this is a weak Bronsted acid:

`NH_4^(+) +H_2O(l) rightleftharpoons H_3O^(+) + NH_3(aq)`

`f.`, you got `"ammonia"`; in aqueous solution this is a weak Bronsted base, that gives equilibrium quantities of hydroxide at equilibrium, i.e.:

`NH_3(aq) + H_2O rightleftharpoons NH_4^+ + HO^-`

Note that I have of course assumed an aqueous solution for each of the acids and bases.

Answer 2

Everything looks perfect, except for (e) and (f)

Explanation:

You've pretty much nailed everything, but `NH_3` and `NH_4^+` are not good at being an acid and base respectively.

In theory, they could probably donate/receive that extra proton, but the compounds they produce (`NH_2^-` and `NH_5^(2+)`) are not very stable. Also, as you do more labs and other work on the topic of acids & bases, you'll see that you never really consider either of these compounds as being both an acid and base.

Hence, I'd say that `NH_3` is just a Brønsted base, and `NH_4` is just a Brønsted acid.

Hope that helps :)