Final answer:
Strong acids completely dissociate into ions in solution, exemplified by hydrochloric acid which fully separates into H+ and Cl- ions. Weak acids only partially dissociate, like those in tomato juice or vinegar. Acid strength is determined by the degree of ionization and is reflected in the acid's pKa value.
Step-by-step explanation:
The difference between strong acids and weak acids lies in their degree of ionization in solution. When hydrochloric acid (HCl) is dissolved in water, for instance, it completely dissociates into hydrogen ions (H+) and chloride ions (Cl-), making it a strong acid since all of the HCl molecules become ions. In contrast, substances like the acids found in tomato juice or vinegar only partially dissociate, indicating that they are weak acids. The strength of an acid is also reflected in its acid constant (Ka) or pKa value, with a smaller pKa denoting a stronger acid.
Acid strength is an important concept as it affects an acid's chemical behavior in reactions, particularly its ability to donate protons. The conjugate base of a strong acid is stable and weak, which is why the acid readily donates its proton, while the conjugate base of a weak acid is relatively stronger and the acid does not dissociate as readily.