CHAPTER 21 SOLUTIONS

21-1 The dissolving process

a solution is a homogeneous mixture(solute in solvent) of

molecules, atoms, or ions that cannot be separated by

filtration

when ionic compounds dissolve in water, the ions become

hydrated and dissociate

an increase in entropy is a driving force in the formation

of many solutions

the more abundant substance in a solution is called the solvent

the solvent dissolves the solute

dissociation is the separation of ions from each other in solution

solvation is the process by which solvent particles surround

solute particles

solvolysis & hydrolysis chem reactions/solvation & hydration no

chemical change NOTE THE DIFFERENCE

21-2 Solvent-solute combinations

polar solvent + polar solute solution is likely

polar solvent + non polar solute solution is not likely

nonpolar solvent + polar solute solution is not likely

nonpolar solvent + nonpolar solute solution is likely

21-3 solids, liquids,a nd gases in solution

miscible(dissolvable) liquids are mutually soluble

immiscible liquids separate into layers after standing awhile

some alloys are solid metal-metal solutions

21-4 solution equilibrium

the point at which the number of particles leaving the crystal

surface equals the number returning to the surface is

called solution equilibrium

saturated solution-undissolved material in container

unsaturated solution-all material dissolved

supersaturated solution-solution holds more solute than a

saturated solution can hold(heating and cooling solution)

precipitate-means to fall out

21-5 Dissolving effects

solution rate is affected by:

surface area exposed to fresh solvent

kinetic energy of particles(heat)

enthalpy of solution is the energy change that occurs when one substance is dissolved in another. Most solids have positive enthalpies of solution/gases have negative

Henry's law: the mass of a gas that will dissolve in a liquid

at a given temperature varies directly with the partial

pressure of that gas

21-6 Concentration

for a solution with a known molarity, a measurement of volume is

also a measure of the number of particles

the concentration of a standard solution is known with a high

degree of certainty

assume 100% dissociation

M=moles of solute/L(cdm) of solution

a 1 molal(m) solution contains 1 mole of solute in 1 Kg of solvent

molal solutions are useful in studying colligative properties

not used in this course very often

m=moles of solute/kg of solvent

mole fraction is a comparison of moles of one component to the

total number of moles of solution

the sum of the mole fractions of all components equals 1

a formal(F) solution contains one gram-formula mass of solute

per L(cdm) of solution. book does not use formal at all

mass percent is used by biologist to express concentration