Cliffs AP Chemistry, 3rd Edition

Answer: D

See the chart on page 158. Any anion derived from a weak acid acts as a base in a water solu-
tion. The carbonate polyatomic anion, CO 3 2–(aq), is derived from the weak acid carbonic acid,
H 2 CO 3. There are no common basic cations.

6. Identify the net ionic product(s) produced when solutions of potassium bicarbonate
   (KHCO 3 ) and hydrobromic acid (HBr) are mixed.

A. KBr and H 2 CO 3

B. H 2 CO 3 , K+, and Br–

C. KBr, H 2 O, and CO 2

D. K+, Br–, H 2 O, and CO 2

E. H 2 CO 3

Answer: E

To write a net ionic equation for an acid-base reaction between two solutions, use the following
three steps:

1. Determine the nature of the principal species in both solutions. KHCO 3 would ionize to
   produce K+and HCO 3 –. HBr would ionize to produce H+and Br–.


2. Determine which species take part in the acid-base reaction. The bicarbonate anion
   (HCO 3 – ) is basic, and the H+from the hydrobromic acid is acidic.


3. Write a balanced net ionic equation. Because H 2 CO 3 is a weak acid, it would tend to re-
   main as carbonic acid, especially in the presence of a strong acid like HBr. KBr is an ionic
   solid, soluble in water; therefore, it would exist as separate ions known as spectator ions,
   which are not written in the net ionic equation.


4. All of the following choices are strong bases EXCEPT

A. CsOH

B. RbOH

C. Ca(OH) 2

D. Ba(OH) 2

E. Mg(OH) 2

Answer: E

All hydroxides of the Group I metals are strong bases. The hydroxides of the heavier Group II
metals (Ca, Sr, and Ba) are also strong bases. Mg(OH) 2 is not very soluble in water, yielding
relatively little OH–(aq).

Acids and Bases