Chem Unit 3

Solution

homogeneous mixture of two or more substances in which each substance retains its chemical identity

solute

component present in the smaller amount

solvent

component present in larger amount

homogenous

Solutes at particle-level are uniformly distributed

Solute generally can be separated from the solvent by

physical processes

Solubility in solids

solubility increases as temperature increases

Solubility in gasses

solubility decreases as temperature increases.

Henry’s Law

Pressure has little effect on solids or liquids in water. For gases, solubility is directly proportional to the partial pressure of the gas above the liquid.

Saturated

Contains the maximum amount of solute that can dissolve; undissolved excess solute is in dynamic equilibrium with dissolved solute

Unsaturated

Contains less than the maximum amount of solute that could dissolve.

Supersaturated

An unstable solution that temporarily holds more dissolved solute than a saturated solution

aqueous solution

uses water as the solvent

Factors making rate of solution formation faster

more surface area, agitation, higher temperature

In general the greater the difference in solute-solvent polarity…

the less soluble is the solute

% by mass

mass solute / mass solution x 100

% by volume

volume solute / volume solution x 100

mass volume %

mass solute / volume solution x 100

add two volumes doesn’t always

equal the entire volume

molarity (M)

moles of solute / liters of solution

Dilution formula

C₁V₁ = C₂V₂

colloidal dispersion

homogenous mixture, spread evenly, particles in solution are slightly larger; NOT a solution, do not use solute or solvent

suspension

heterogenous mixture, particles are very large in size, particles will settle at the bottom

Tyndall effect

solution: light will pass through; colloid: light will pass through but scatter; suspension: light will not pass through

Colligative property of a solution

physical property of solution depends only on the number of solute particles present, not on their chemical identity; it is the total number of particles present in solution that determines the magnitude of a colligative property effect

Vapor pressure

pressure exerted by vapor above liquid when in physical equilibrium (rate of evaporation = rate of condensation)

Colligative properties

adding a nonvolatile solute lowers the vapor pressure due to surface displacement, compared to pure solvent; when solute disrupts alignment of particles, freezing point is lowered

Osmosis

the passage of solvent through a semipermeable membrane from a dilute solution (or pure solvent) toward a more concentrated solution. A semipermeable membrane allows small solvent molecules through but blocks larger solute particles. Osmosis only implies solvent movement

How is osmosis stopped

when concentrations are equal or when right is so big it stops movement from left

Osmosis pressure

pressure that must be applied to prevent the net flow of solvent through a semipermeable membrane from a solution of lower solute concentration to a solution of higher solute concentration

Osmolarity =

molarity x i, where i is the # particles produced per formula unit in dissociation

what is osmolarity

lets two solutions of different molarity and different solute identity to be compared on same basis for osmotic pressure

redox reaction

oxidation reduction, transfers electrons from one reactant to another

nonredox reaction

involves no transfer of electrons between reactants

oxidation is the ____ of one or more electrons by a reactant, reduction is ____ of one or more electrons by a reactant

oxidation is losing, reduction is gaining

a reduced element is an _____ agent, oxidized element is ____ agent

reduced is oxidation agent, oxidized is reduction agent

collision theory

reactant particles must come in contact with each other, colliding particles must carry a minimum combined kinetic energy and activation energy, particles must collide in favorable orientation

enthalpy ∆H

amount of energy absorbed or released during a reaction

∆H < 0 is

exothermic

∆H > 0

endothermic

entropy ∆S

measure of randomness or disorder

∆S > 0

more disorder as final product

Gibbs Free Energy ∆G definition

a way to connect enthalpy to entropy, measures spontaneity

Gibbs free energy equation

∆G = ∆H - T∆S

∆G<0, ∆G=0, ∆G>0

spontaneous and exergonic, equilibrium, nonspontaneous and endergonic

Arrhenius Acid- Base Theory

acid has H⁺, base has OH⁻

Bronsted Lowry Acid Base Theory

acids donate protons (H⁺), base accepts a proton (H⁺)

ionization (acid)

ions produced from a molecular compound dissolved in solution

dissociation (base)

ions already present in an ionic compound separate in solution

strong acids

HCl, HBr, HI, HNO₃, HClO₃, HClO₄, H₂SO₄

strong base

LiOH, NaOH, RbOH, CsOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂

Ka

acid ionization constant that quantifies weak acid strength

Kb

strength of a base

self ionization of water (amphiprotic)

H₂O + H₂O ⇌ H₃O⁺ + OH⁻

pH =

-log[H₃O⁺]

pOH =

-log[OH⁻]

pOH + pH =

14

[H₃O⁺] = [OH⁻] = 1.00 × 10⁻⁷

neutral solution

[H₃O⁺] > [OH⁻]

acidic

[H₃O⁺] < [OH⁻]

basic

pKa =

-logKa

at equilibrium, weak acid ionization process is ___ favored

reactant

strong acid - strong base salt

neutral salt

strong acid weak base salt

acidic salt

weak acid - strong base salt

basic salt

weak acid weak base salt

weak acid weak base salt

acid + water

acidic solution

base + water

basic solution

salt hydrolysis reaction

salt + H₂O → H₃O⁺ and/or OH⁻

buffer solution

resists large pH changes when small amounts of acid or base are added. Contains conjugate acid base pair in the same solution

Henderson Hasselbach equation

buffer pH = log [conj base] / [weak acid]

strong electrolyte

fully ionizes and dissociates (strong acid and base)

weak electrolyte

partially ionizes / dissociates (weak acid and base)