Which of the following statements best describes the main difference between a strong acid and a weak acid?

• A. A strong acid is always more corrosive than a weak acid.
• B. A strong acid has a lower concentration than a weak acid.
• C. A strong acid has a higher $pH$ than a weak acid.
• D. A strong acid completely dissociates in water, while a weak acid only partially dissociates.

Answer: (D)

Verified step by step guidance

1. Understand the concept of acid dissociation: In chemistry, the strength of an acid is determined by its ability to dissociate in water. A strong acid completely dissociates into its ions, while a weak acid only partially dissociates.
2. Consider the dissociation process: For a strong acid, the dissociation can be represented as \( HA \rightarrow H^+ + A^- \), where \( HA \) is the acid, \( H^+ \) is the hydrogen ion, and \( A^- \) is the conjugate base. This reaction goes to completion.
3. Compare with weak acid dissociation: For a weak acid, the dissociation is represented as \( HA \rightleftharpoons H^+ + A^- \). This indicates an equilibrium where not all \( HA \) molecules dissociate, resulting in a mixture of \( HA \), \( H^+ \), and \( A^- \).
4. Evaluate the implications on pH: The complete dissociation of strong acids results in a higher concentration of \( H^+ \) ions, leading to a lower pH. Conversely, weak acids have fewer \( H^+ \) ions in solution, resulting in a higher pH compared to strong acids.
5. Clarify misconceptions: The corrosiveness of an acid is not solely determined by its strength. Concentration and specific chemical properties also play roles. Similarly, the concentration of an acid does not define its strength; rather, it is the degree of dissociation that matters.