Which statement about weak acids is false?

Which statement about weak acids is false?

• A. They partially dissociate in water
• B. Their Ka is less than 1
• C. They have Ka less than or equal to 1
• D. They have Ka greater than 1

Answer: (D)

Weak acids only partially dissociate in water because their dissociation equilibrium lies to the left. The dissociation constant Ka = [H+][A−]/[HA] quantifies how far that equilibrium lies toward products. For a weak acid, Ka is less than 1, meaning [H+] and [A−] are small relative to the undissociated HA. That makes statements about partial dissociation and Ka ≤ 1 true. If Ka were greater than 1, the acid would dissociate essentially completely, behaving as a strong acid, which contradicts the definition of a weak acid. So the false statement is the one claiming Ka > 1.

Weak acids only partially dissociate in water because their dissociation equilibrium lies to the left. The dissociation constant Ka = [H+][A−]/[HA] quantifies how far that equilibrium lies toward products. For a weak acid, Ka is less than 1, meaning [H+] and [A−] are small relative to the undissociated HA. That makes statements about partial dissociation and Ka ≤ 1 true. If Ka were greater than 1, the acid would dissociate essentially completely, behaving as a strong acid, which contradicts the definition of a weak acid. So the false statement is the one claiming Ka > 1.