Chapter 9Solutions

DE Chemistry – King William High School

1. Solutions

…are homogeneous mixtures Solute (Kool-Aid) + solute (water) “like dissolves like”…(polar dissolves

polar & nonpolar dissolves nonpolar) Why does oil not mix with water?

Dissociation equations

Ionic solids break up into their ions in water through a process called hydration (water molecules surround them)

EX: NaCl

EX: CaCl2

2. Electrolytes

Electrolytes dissociate in water and can produce an electric current

IONIC Strong electrolytes completely

dissociate EX: MgSO4

Weak electrolytes partially dissociate EX: NH4OH

Nonelectrolytes

Do NOT separate into ions in water and therefore do NOT conduct an electric current

COVALENT EX: sugar (sucrose)

3. Solubility

Saturated solution - contains the maximum amount of solute that can dissolve in the solvent

Unsaturated solution – is dilute…can hold more solute

Solubility Curves

Temperature & solubility

The hotter a solution is…the more solute you can dissolve

Supersaturated solutions – contains more solute than its solubility allows

Henry’s Law

The solubility of a gas in a liquid (CO2 in your soda) is directly proportional to the pressure of the gas above the liquid

Why does your soda go “flat” after it has been opened?

Solubility rules

Page 294; Table 9.8 EX: K2S

EX: Ca(NO3)2

EX: PbCl2

EX: AlPO4

4. Concentrations

Mass percent =

EX: What is the mass percent of NaOH in a solution prepared by dissolving 30.0 g NaOH in 120.0 g of water?

Molarity

M = mol/L EX: What is the molarity of 60.0 g of

NaOH in 250 mL of solution?

5. Dilution calculations

MV = MV What volume of 18.0 M HCl do you

need to prepare 500 mL of 2.0 M HCl?

6. Properties of solutions

Colloids – are homogenous mixtures where the particles are bigger than solute particles…and they do not “settle” out of solution

Colloid examples on page 305 – table 9.12

Suspensions – heterogeneous mixtures (their particles tend to “settle” out over time