In chemistry, the terms “Strong” and “Weak” when talking about acids and bases refer strictly to the extent of dissociation (ionisation) in aqueous solution.
Strong Acids
Definition: Strong Acid
A strong acid is a proton donor that fully dissociates in aqueous solution.
Example:
Strong Base
Definition: Strong Base
A strong base is a proton acceptor that fully dissociates in aqueous solution.
Example:
Weak Acid
Definition: Weak Acid
A weak acid is a proton donor that partially dissociates in aqueous solution.
Example:
Weak Base
Definition: Weak Base
A weak base is a proton acceptor that partially dissociates in aqueous solution.
Example:
Critical Concept: Strength determines Rate, Stoichiometry determines Yield
Do not confuse “Weak” with “Less Product”.
In a reaction like Mg + Acid:
- Strong Acid (HCl): Fully dissociated. High
immediately. Fast rate. - Weak Acid (CH₃COOH): Partially dissociated. Low
initially. Slow rate. Why the yield is the same: As the magnesium consumes the available free
ions, the concentration of product increases and reactants decreases. According to Le Chatelier’s Principle, the equilibrium of the weak acid shifts to the right to restore balance: As soon as an is used up, the weak acid dissociates to replace it. This continues until all the weak acid molecules are eventually consumed. General Rule: Provided the reaction goes to completion (e.g., gas evolves, precipitate forms, or using excess reagents), the total yield is determined strictly by the moles of limiting reactant (Stoichiometry), never by the dissociation constant (
or Strength) of that reactant.