Question

A weak acid placed in water contains

a. the same number of unionized acid molecules as a strong acid in water.
b. no unionized acid molecules.
c. a lower concentration of unionized acid molecules than a strong acid in water.
d. a higher concentration of unionized acid molecules than a stronger acid in water

Answer 1

Answer is: d. a higher concentration of unionized acid molecules than a stronger acid in water.

For example:

Chemical reaction 1: HCl(aq) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq).

Chemical reaction 2: CH₃COOH(aq) + H₂O(l) ⇄ H₃O⁺(aq) + CH₃COO⁻(aq).

Hydrochloric acid (HCl) is strong acid, which means that concencentration of hydronium ions are equal as concentration of hydrochloric acid.

Acetic acid (CH₃COOH) is weak acid and does not dissociate completely as HCl, so concentration of hydronium ion in this solutions are very low.

Answer 2

The correct answer is option D. A weak acid placed in water contains a higher concentration of unionized acid molecules than a stronger acid in water. A weak acid is a type of acid that doesn't completely dissociates into ions. Examples are carbonic acid and acetic acid.