Chapter 13 - Properties of Solutions

Solutions

Homogeneous mixtures of two or more pure substances

Solute

Part being dissolved

Solvent

Thing that dissolves

Solvation

Dissolving process

Hydration

The dissolving process with water as the solvent

Substances depend on what to form solutions

Intermolecular forces and their natural tendency to mix

Solute-solute interactions

Must be overcome to disperse these particles when making a solution

Solvent-solvent interactions

Must be overcome to make room for the solute

Solvent-solute interactions

Occur as the particles mix

ΔH solvent

Energy required to vaporize

Solubility

How much solute can be dissolved in a given amount of solvent at a given temperature

Saturated solutions

Cant add more solute

Unsaturated solutions

Can add more

Supersaturated solutions

Temporary situation where the solution is cooled slowly and for it to react, a crystal from the solute is added

Factors that affect solubility

• Solute-solvent interactions

• Temperature

• Pressure (for gas solutes only)

pressure effects on solids and liquids

the solubility isn’t affected

pressure effects on gases

Solubility is affected by pressure

Henrys Law

The solubility of a gas is proportional to the partial pressure of the gas above the solution

Henry’s Law for two points

Temperature effects on solid’s solubility

for most solids, as temperature increases, solubility increases

Temperature effects on gases’s solubility

As temeprature increases, solubility decreases

Mass percentage (% m/m)

Parts per million (ppm)

Parts per billion (ppb)

Mole fraction (X)

Molarity (M)

Molality (m)

Colligative properties

They depend only on the quantity, not on the identity of the solute.

what are the colligative properties

vapor pressure reduction

boling point elevation

freezing point depression

osmotic pressure

Vapor pressure reduction (Raoult’s Law)

Boiling point elevation

i

Van-Hoff factor, the number of ions you get when dissolving the compound

Freezing point depression

Osmosis

The net movement of solvent molecules from a solution of low to a high concentration of solute across a semipermeable membrane

Semipermeable membrane

Smaller particles pass through it, but it blocks larger particles

Osmotic pressure

The applied pressure to stop bigger particles

Colloids

Suspension of particles larger than individual ions or molecules, but too small to be settled by gravity.