13.4 Equilibria for Weak Acids and Bases

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pH Calculations for Weak Acids & Bases

weak acids and bases
Acid Ka
HF 6.8 × 10-4
HC2H3O2 1.76 × 10-5
HCN 4.9 × 10-10

KaKb = Kw
A stronger acid has a larger Ka / smaller pKa.
A stronger base has a larger Kb / smaller pKb.
The stronger the acid, the weaker the conjugate base and vice versa.

What is the pH of a 0.1M solution of acetic acid (Ka = 1.76 × 10-5)?

What is the Ka of a weak acid, HA, if the pH of a 0.1M solution is 3?

What is the pH of a 0.1M solution of ammonia (Kb = 1.75 × 10-5)?