For conjugate acid-base pairs, how are Ka and Kb related?
Consider the reaction of acetic acid in water.
where
a. Which two bases are competing for the proton?
b. Which is the stronger base?
c. In light of your answer to part b, why do we classify the acetate ion (CH3CO2-) as a weak base? Use an appropriate reaction to justify your answer.
In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid.
To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1x106, calculate Kb for the conjugate base of this strong acid. Why do conjugate bases of strong acids have no basic properties in water? List the conjugate bases of the six common strong acids. To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acid properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a ______ base. The conjugate acid of a weak base is a ______ acid. The conjugate base of a strong acid is a ______ base. The conjugate acid of a strong base is a ______ acid. (Hint: Weak gives you weak and strong gives you worthless.)
