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

2 Answers
May 11, 2017

Answer:

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.

May 11, 2017

Answer:

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 :)