Everything Science Grade 10

18.2 CHAPTER 18. REACTIONS IN AQUEOUS SOLUTION

DEFINITION: Dissociation

Dissociation is a general process in which ionic compounds separate into

smaller ions, usually in a reversible manner.

DEFINITION: Dissolution

Dissolution or dissolving is the process where ionic crystals break up into

ions in water.

DEFINITION: Hydration

Hydration is the process where ions become surrounded with water molecules.

Cl Na

Figure 18.3: Sodium chloride dissolves in water

The dissolution of sodium chloride can be represented by the following equation:

NaCl (s)→Na+(aq)+Cl−(aq)

The dissolution of potassium sulphate into potassium and sulphate ions is shown below as
another example:

K 2 SO 4 (s)→ 2 K+(aq)+SO^24 −(aq)

Remember thatmolecularsubstances (e.g. covalent compounds) may also dissolve, but
most will not form ions. One example is glucose.

C 6 H 12 O 6 (s)→C 6 H 12 O 6 (aq)

316 Chemistry: Chemical change