Final answer:
The assertion that water is ionized before dissociation is false; water autoionization is a separate and very limited process. Dissociation of ionic compounds results from their interactions with water molecules.
Step-by-step explanation:
The statement that water is already ionized before dissociation occurs is false. Water in its pure state is largely composed of neutral H₂O molecules. However, a very small fraction of these molecules undergo autoionization, which is a process where two water molecules react to form a hydroxide ion (OH⁻) and a hydrogen ion (H⁺), which immediately associates with another water molecule to form a hydronium ion (H₃O⁺).
When ionic compounds such as NaCl dissolve in water, the Na⁺ and Cl⁻ ions that form are not a result of water itself being ionized beforehand but rather the ions are released as the ionic bonds are disrupted by interaction with water's polar molecules. We observe that the positive Na⁺ ions are surrounded by the negatively charged oxygen atoms of water, and the negative Cl⁻ ions are surrounded by the positive hydrogen atoms.
Thus, the dissociation of water molecules to form ions is an entirely separate process and occurs to a very small extent in pure water, characterized by the ion-product constant for water (Kw). Conversely, the dissolution process of an ionic compound like NaCl in water is governed by the interactions between the ions and the water molecules, leading to the ions being surrounded by a hydration shell.