Chapter 12: Solutions

Chem 2

solutions

homogenous mixtures of two or more pure substances. solute is dispersed uniformly throughout the solvent

solute

substance that dissolves

solvent

major component of the solution

concentration

amount of solute that is present in a solution

solution contains small amount of solute

dilute

solution contains a large amount of solute

concentrated

solution contains the maximum amount of dissolved solute

saturated

mass %

mass of solute / mass of solution x 100%

volume percent

volume of solute / volume of solution x 100%

mass/volume %

mass of solute / volume of solution x 100%

ppm equation - expressing very small concentrations

mass of solute / mass of solution x 10⁶

ppb equation - expressing very small concentrations

mass of solute / mass of solution x 10⁹

Molarity (M) equation - describing chemical reactions

moles solute / liter solution

molality (m) equation - describing physical properties

moles solute / kg solvent

mole fraction (x) - describing physical properties

moles of solute / total moles solution

equation to solve for moles

moles = MV

dilution equation

M₁V₁ = M₂V₂

factors that affect solubility

solute-solvent interactions, pressure (for gaseous solutes), temperature

solute-solvent interactions

“like dissolves like”, the stronger the solute-solvent interaction, the greater the solubility of a solute in that solvent

no ions present, no polar molecules present

dispersion forces only

no ions present, yes polar molecules present, no H atoms bonded to N,O,F atoms

dipole-dipole forces

no ions present, yes polar molecules present, yes H atoms bonded to N,O,F atoms

hydrogen bonding

yes ions present, yes polar molecules present

ion-dipole forces

yes ions present, no polar molecuels present

ionic bonding

electrolytes

ionic compounds, acids. compounds that produce ions in solution

nonelectrolytes

most covalent compounds

enthalpy

entropy

determines whether a change happens spontaneously, a tendency toward disorder or mixing

exothermic

endothermic

low gas pressure

lower solubility

high gas pressure

higher solubility

henry’s law

S = kP

ideal solution

number of particles per formula unit if complete dissociation occurs

real solution

number of particles that actually form

colligative properties

depend on the number of particles in a solution, not on the type of particle

osmotic pressure equation

pie = iMRT - i: van’t hoff factor, M: molarity, R: 0.0821Lamt/molK

osmotic pressure

water flows toward a higher pie value

what is this

hypertonic

what is this

isotonic

what is this

hypotonic

freezing point depression

presence of solute lowers the freezing point of a liquid. freezing point of a solution drops as more solute is added

freezing point depression equation

delta T_f = imK_f - i: van’t hoff factor, m: molality, K_f: constant

vapor pressure

pressure of the gas above the liquid at dynamic equilibrium

solutions with nonvolatile solutes

vapor pressure of the solution is less than that of pure water

raoult’s law (nonvolatile solute)

P_{soln ⁼} (X_solvent)(P_solvent)

solutions with volatile solutes

P_total = {X_iP_i

distillation

colloids

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