The [H3O+] of a solution with pH = 3 is

-10 M.
10 M.
1 x 10-3 M.
1 x 103 M.
1 x 10-11 M.

Identify the acid(s) and base(s) in the following reaction:

CH3COOH(aq) + NH3(aq) CH 3COO-(aq) + NH4+(aq)

CH3COOH is the only acid, and NH3 is the only base.
CH3COOH is the only base, and NH3 is the only acid.
CH3COOH and NH4+ are acids, and NH3 and CH3COO- are bases.
CH3COOH and NH3 are acids, and NH4+ and CH3COO- are bases.

1 answer

For 1, pH = -log(H^+). Plug and chug. If you don't understand how to do this, explain your exact problem and I can help you through it. (It may be so simple that you just don't know how to handle the calculator.).

#2. No arrow. I don't know the reactants from the products. But the answer is to apply the Bronsted-Lowry theory of acids/bases.
Remember,
HA + H2O ==> H3O^+ + A^-

So HA is an acid because it donates a proton (to H2O) to form A^- (the conjugate base of HA) while H2O is a base (it accepts a proton from HA) and it forms the conjugate acid(H3O^+).