CH110

Chapter 12 Notes

In chapters 1, 3, & 4, we explored general terminology and reactions of solutions. We now return back to solutions to explain some physical phenomena, such as why impure water (a solution of ethylene glycol, aka antifreeze) is used as a car coolant instead of just pure water.

Solutions can be of several types: gas-gas, gas-liquid, liquid-liquid, solid-liquid, gas-solid, solid-solid (and, for completeness, one would suppose, combinations with the other 2 phases of matter as well)

see Fig of mouse breathing "underwater" on page 510- why is the compound fluorine-containing when F is a highly toxic cumulative bone-marrow attacker?

Molarity revisited- moles solute per liter solution (molality is moles solute per kg solvent)

For mass percent, volume percent, mole percent or mole fraction, ppm and ppb calculations, DON'T FORGET THE UNITS!

ppm = mg/L

ppb = ug/L

ppt = ng/L

Look at Figure 12.1 on page 513 and see why analysis of low concentrations can be so challenging.....femptomolar (10^-14) analysis IS possible, luckily, since sometimes compounds are toxic at ppq levels!! (e.g.- dioxin)

M is T dependent....see Fig. 12.2....why??

Dissolution can be endothermic or exothermic ("cold packs" (NH₄NO₃)(what else is this used for?) and "hot packs" (MgSO₄))

Enthalpy of solution (Fig. 12.4)

Nonideal solutions can expand or contract upon dissolution.....why??

Why do things dissolve?

LIKE DISSOLVES LIKE (see Fig. 12.7)

Fully dissolving compounds are said to be miscible

Saturated solution- dynamic equilibrium

Solubility vs. temperature- supersaturation

Purification by supersaturation

Gas solubility

Temperature- no general rule though most gases are less soluble in water at higher temperature

Pressure- higher pressure = higher solubility due to equilibrium = Henry's Law (will see again in P.Chem)...very common example?

Colligative properties- depend on the number of solute particles present, NOT their identity

Vapor pressure- Raoult's Law

Important application in fractional distillation....used in chemical purification, oil refining, ethanol production, etc.

Freezing point depression

Boiling point elevation

Osmotic pressure