Partial Dissociation Defines Weak Acids

Steps:

• Recall that acids are classified by dissociation extent in water: strong acids fully ionize, weak acids partially ionize.
• Examine option A: it states some molecules dissociate, matching partial ionization.
• Check other options for accuracy against acid properties like reactivity and pH.
• Identify A as correct since it aligns with the equilibrium dissociation constant (Ka) for weak acids.

Why A is correct:

• Weak acids partially dissociate per the equilibrium HA ⇌ H⁺ + A⁻, where only some molecules ionize, unlike strong acids.

Why the others are wrong:

• B: Weak acids do react with carbonates, producing CO₂, though slower than strong acids.
• C: Weak acids can form concentrated or dilute solutions; strength is about ionization, not concentration.
• D: Weak acids have higher pH than strong acids of same concentration due to less H⁺ production.

Final answer: A