Polar water molecules interacting with positive and negative ions of a saltPolar water molecules interacting with positive and negative ions of a salt ..

SolvationSolvationSolvent molecules attract

solute particles.Solute particles break away

from each other and the crystal structure breaks apart.

The ethanol molecule contains a polar O—H bond.The ethanol molecule contains a polar O—H bond.

The polar water molecule interacts strongly with the polar O—H The polar water molecule interacts strongly with the polar O—H bond in ethanol.bond in ethanol.

An oil layer floating on waterAn oil layer floating on water

Dissociation EquationsDissociation Equations

Non-electrolytes in solution separate into individual neutral, molecules that move freely throughout the solution. An equation showing a non-electrolyte dissolving simply shows it changing from the pure to its dissolved state.

C12H22O11(s) → C12H22O11(aq)

Dissociation EquationsDissociation Equations

When electrolytes dissolve they separate into ions that move freely throughout the solution.

The solution as a whole remains neutral, since, although the individual ions are charged, they balance each other out.

Equations that show electrolytes dissolving show the solute changing from its pure state to aqueous ions.

Dissociation EquationsDissociation Equations

These equations are called dissociation equations.

Dissociation equations must be balanced, show correct ionic charge and physical states.

KCl(s) ↔ K+(aq)

+ Cl-(aq)

Al2(SO4)3(s) ↔ 2 Al3+(aq)

+ 3 SO42-

(aq)

Cu(NO3)2(s) ↔ Cu2+(aq)

+ 2 NO3-(aq)

Ionize Vs. DissociateIonize Vs. Dissociate

Dissociation – when ionic compounds break apart

Ionize – when molecules break apart

HCl(g) ↔ H+(aq) + Cl-

(aq)

NaOH(s) ↔ Na+(aq) + OH-

(aq)

► Practice, p.198 # 2

In any chemical reactionIn any chemical reaction

REACTANTS → PRODUCTS

Energy must be absorbed to break the chemical bonds of the reactant molecules.

AND

Energy must be released when the chemical bonds are formed in the building of the product molecules.

CC33HH88 (g)(g) + O + O22 (g)(g) → CO→ CO22 (g)(g) + H + H22O O (g)(g)1 3 45

Represent the molecules with structural formulae

O = O

O = O

O = O

O = O

O = O

→

O = C = O

O = C = O +

O = C = O

H

H – C – H

H – C – H +

H – C – H

H

H – O – H

H – O – H

H – O – H

H – O – H

Bond Type Energy (kJ/mol)

C - C 348

C - H 415

O = O 499

C = O 742

O - H 465

► Section 5.2 #1 – 4, 8