Chapter 12 | Solutions

Henry’s law

c = kP

c is the concentration (M) of the dissolved gas

P is the pressure of the gas over the solution

k is a constant for each gas (mol/L●atm) that depends only on temperature

Molarity (M)

moles of solute / liters of solution

Mass percentage of solute

(grams of solute / grams of solution) x 100%

Molality (m)

moles of solute / kg of solvent

Raoult’s Law

P_solution < P°_solvent

P_solution = X_solventP°_solvent

Boiling-point elevation

ΔT_b = mK_b

Freezing-point depression

ΔT_f = mK_f

ΔT_f​ = T_{f pure}​−T_{f solution}

Mole fraction

X = moles of solute / total moles of solution

Osmotic Pressure

π = MRT

π = osmotic pressure

M = molarity

R = gas constant = 0.082 (L • atm/ mol • K)

T = temperature in K

Colligative Properties of Electrolyte Solutions

Boiling-Point Elevation: ΔT_b = iK_bm

Freezing-Point Depression: ΔT_f = -iK_fm

Osmotic Pressure (π): π = iMRT

Van’t Hoff Factor

i = total number of ions separated from an ionic compound

Solution

A homogenous mixture of 2 or more substances

Solute

The substance (s) present in the smaller amount (s)

Solvent

The substance present in the larger amount

Solubility

The amount that dissolves in a given quantity of solvent at a given temperature

“like dissolves like”

Two substances with similar intermolecular forces are likely to be soluble in each other

Miscible

Fluids that mix with or dissolve in each other in all proportions

Immiscible

Fluids that do not dissolve in each other

Solubility of gases

More soluble at high temperatures and low pressure

Solubility of solids

Solubility increases at higher temperatures

Phase diagram