Cliffs AP Chemistry, 3rd Edition

3. Arrange the following oxyacids in order of decreasing acid strength.

HClO, HIO, HBrO, HClO 3 , HClO 2

A. HClO > HIO > HBrO > HClO 3 > HClO 2

B. HClO > HClO 2 > HClO 3 > HBrO > HIO

C. HIO > HBrO > HClO > HClO 2 > HClO 3

D. HBrO > HClO > HClO 3 > HClO 2 > HIO

E. HClO 3 > HClO 2 > HClO > HBrO > HIO

Answer: E

For a series of oxyacids of the same structure that differ only in the halogen, the acid strength
increases with the electronegativity of the halogen. Because the electronegativity of the halogens
increases as we move up the column, the order at this point would be HClO > HBrO > HIO. For
a series of oxyacids containing the same halogen, the HO bond polarity, and hence the acid
strength, increases with the oxidation state of the halogen. Therefore, in the series HClO, HClO 2 ,
and HClO 3 , the oxidation states of the chlorine are +1, +3, and +5, respectively. And thus the
correct order for decreasing acid strength is HClO 3 > HClO 2 > HClO > HBrO > HIO.

4. Given the following reversible equation, determine which species is or are Brønsted acids.

CO 332 - _aqi++H O 2 ^,hEHCO-_aqi OH-]aqg

A. CO 32 - (aq)

B. H 2 O(,) and OH–(aq)

C. H 2 O(,) and HCO 3 - (aq)

D. CO 32 - (aq)and OH–(aq)

E. H 2 O(,)

Answer: C

Brønsted acids donate protons (H+). In the equation, both H 2 O and HCO 3 – donate H+.

5. Which of the following salts contains a basic anion?

A. NaCl

B. Ba(HSO 4 ) 2

C. KI

D. Li 2 CO 3

E. NH 4 ClO 4

Part II: Specific Topics