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The process whereby ionic or molecular compounds dissolve = DISSOLUTION.

Two types of dissolution processes:

1. Dissociation

2. Ionization

Dissociation = Separation of an ionic compound’s cations and anions by the process of solvation.

E.g.

NaCl (s) —> Na+ (aq) + Cl- (aq)

Ionization = The formation of cations and anions from a covalent compound that reacts with H₂O.
E. g.

HCl(g)+H₂O(l) —> H₃O⁺(aq) +Cl⁻(aq)

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The breaking up of existing ions.

Dissociation of salts by solvation in a solution = The separation of the anions and cations.

SOLVATION = The process of any solvent surrounding ions of a solute in solution.

HYDRATION = The process of water surrounding ions of a solute in solution.

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The formation of completely new ions.

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Identify the type of dissolution for each substance below, and write down the equation for the dissolution each compound:

HCl

KF

Mg(OH)₂

H₂SO₄

NH₃

AlCl₃

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Why do substances dissolve (become miscible)?

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Why do substances dissolve (become miscible)?

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1. When a solute dissolves, it’s particles proceed towards a state of greater DISORDER.

2. At the same time the solvent (a pure homogeneous substance) also becomes mixed with particles of a different kind.

3. There is an overall increase in disorder (called entropy), which is the driving force in the dissolution process.

4. Despite this increase in disorder, which aids dissolution, not all substances dissolve.

5. Two substances mix perfectly into solution (i.e. dissolve) iff:

INTERMOLECULAR FORCES between the molecules/ions of the substance are OVERCOME.

Therefore, when the forces between the molecules of the solute and solvent are of the same ORDER OF MAGNITUDE, then the molecules of the solvent can take the place of the molecules of the solute.

The result = MIXING.

LIKE DISSOLVES LIKE.

Molecular crystals dissolve in non-polar solvents => solute forms Vd Waals LONDON Forces with solvent.

Ionic compounds dissolve in polar solvents => ions of solute form ION-DIPOLE interactions with solvent.

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Hydrogen Bonds - What Are Hydrogen Bonds - How Do Hydrogen Bonds Form

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Properties of water due to hydrogen bonding 

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Properties of water due to hydrogen bonding 

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High surface tension

High heat capacity

Capillary action due to cohesion and adhesion forces

Density change due to change in temperature

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Due to VSEPR

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4.3 Describe the structure of and bonding in silicon and silicon dioxide [SL IB Chemistry]

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The difference between diamond and graphite, giant covalent structures