Cliffs AP Chemistry, 3rd Edition

Samples: Multiple-Choice Questions

1. What is the OH–concentration (M) of a solution that contains 5.00 × 10 –3mole of H+per
   liter? Kw=1.00 × 10 –14.

A. 7.00 × 10 –14M

B. 1.00 × 10 –12M

C. 2.00 × 10 –12M

D. 1.00 × 10 –11M

E. 2.00 × 10 –11M

Answer: C

[H+][OH–] = 10–14. Substituting gives (5.00 × 10 –3)(x) = 10–14. Solving for xyields
x= 2.00 × 10 –12.

2. Given the following equation, identify the conjugate acid found in the products.

NH 32 _gaqaqi++H O^,h"NH+- 4 __iiOH

A. NH 3

B. H 2 O

C. NH 4 +

D. OH–

E. H+

Answer: C

The conjugate acid of a base is formed when the base acquires a proton from the acid. In this
reaction, water acts as an acid because it donates a proton to the ammonia molecule. The am-
monium ion (NH 4 +) is the conjugate acid of ammonia (NH 3 ), a base, which receives a proton
from water. The hydroxide ion (OH–) is the conjugate base.

Acids and Bases