Ka measures the extent of acid ionization; larger Ka means a stronger acid.
Practise Acids, Bases & Electrochemistry All Acids, Bases & Electrochemistry topics
The acid dissociation constant Ka is the equilibrium constant for HA <-> H+ + A-, written as Ka = [H+][A-]/[HA]. Its negative logarithm is pKa, and a smaller pKa means a stronger acid. When the pH equals pKa, the concentrations of the acid and its conjugate base are equal, a fact that underpins buffer design. Ka values depend on temperature and ionic strength, but they are normally tabulated at 25 C in dilute water. Chemists use Ka to predict how much of an acid is ionized at a given pH.
Key ideas: Ka = [H3O+][A-]/[HA] at equilibrium; pKa = -log Ka. Lower pKa means stronger acid, and a drop of one pKa unit is a tenfold increase in strength. When pH equals pKa, [A-] equals [HA]. Ka changes with temperature but not with concentration.
Common mistakes and connections: Mistakes include putting water in the expression, using initial rather than equilibrium concentrations, and thinking a larger pKa means stronger acid. Ka is unitless in thermodynamic form but often quoted with mol/L. It connects directly to Henderson-Hasselbalch, indicator ranges and acid-strength ordering.
Lower pKa means a larger Ka and a stronger acid, so HF (3.17) is stronger than acetic acid (4.76), and HCN and phenol are very weak. The interactive lesson shows this as a live animation or chart.
Acetic acid has a pKa of 4.76, while hydrofluoric acid has a pKa of 3.17, so HF is the stronger acid.
Ka measures the extent of acid ionization; larger Ka means a stronger acid.
Acid Dissociation Constant is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Acids, Bases & Electrochemistry first: Strong Bases, Weak Acids, Weak Bases.
The next topics in Acids, Bases & Electrochemistry are Ka and Kb Relationship and Percent Ionization.
Yes. The interactive lesson includes a self-check question on Acid Dissociation Constant, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Acid Dissociation Constant is topic 13 of 105 in Acids, Bases & Electrochemistry.