acids and bases

[delorfilinde]

A student used 40.0 mL of 0.10 mol/L HBr(aq) to neutralize 20.0 mL of a 0.10 mol/L basic solution. The most likely formula for the basic solution would be

A. KOH(aq)
B. HOOCCOOH(aq)
C. Sr(OH)2(aq)
D. NH3(aq)

How would I go about figuring this out?

[sdekivit]

there is only half the amount of mols base needed to neutralize the acid --> the base needs to be capable of taking up 2 protons.

--> C

(B is an acid and therefore wrong. KOH will dissolve yielding 1 mol OH(-) per mol KOH and NH3 can take up only 1 proton.

--> Sr(OH)2 yields two mol OH(-) per mol Sr(OH)2 and therefore only half the amount of mol Sr(OH)2 is needed two neutralize the acid)