What about the second statement? Because HI is a
strong acid it will donate, not accept, H+ ions. Both
statements are false.- C Conjugate acids and bases appear on the right side of the equation,
so eliminate (A) and (B). A conjugate acid donates an H+ ion. Does either
H 2 O or NO 3 − do that? Yes: H 2 O donates an H+ ion to NO 3 − to re-form the
reactants HNO 3 and OH−. So H 2 O is the conjugate acid, and the answer is
(C).
- A We know that if we fully titrate an acid we need equal amounts of
H+ and OH− ions. There are 2 moles of OH− ion for each mole of Ba(OH) 2 ,
and we’re dealing with 0.015 L of a 0.015 M solution, so
(2)(0.015)(0.015) = 0.00045 moles OH−
We need 0.00045 moles of H+ ion, too. We have 0.03 L
of the HCl solution, and there’s just 1 mole of H+ ion
per mole of HCl, so(1)(0.03)(x) = 0.00045 moles OH−x = 0.015 MChoice (A) is the correct answer.- D H 3 PO 4 looks like the formula of an acid, and it is—phosphoric acid.
Choices (B), (C), and (E) are properties of bases, so eliminate them. Is
H 3 PO 4 on our list of strong acids? No; so it must be a weak acid. Would a
weak acid have a large Ka? No; so eliminate (A). A weak acid is a weak
electrolyte. Choice (D) is the correct answer.