exam 2

dynamic equilibrium

condition where in the rates of the forward and reverse reactions are equal, does not mean the concentrations of reactants and products are equal

Law of mass action

the relationship between the chemical equation and the concentration of reactants and products

Favors products (Keq)

Keq » 1

favors reactants (Keq)

Keq « 1

Q > K

products will decrease and reactants will increase

Q < K

products will increase and reactants will decrease

2A +B +6C = 3D +2E if [A] increases

shifts to the products, B decreases, D and E increase

2A +B +6C = 3D +2E if [E] increases

shifts to the reactants, D decreases, A and B increase

2A +B +6C = 3D +2E if [E] decreases

shifts to the products, D increases, A and B decrease

2A (g) +B(aq) +6C(s) = 3D(g) +2E (aq) if Vol is increased

will shift to the reactants because there is less mol’s of gas

2A (g) +B(aq) +6C(s) = 3D(g) +2E (aq) if Vol is decreased

will shift to the products because there is more mol’d of gas

2A (g) +B(aq) +6C(s) = 3D(g) +2E (aq) + heat

If temp increases: will shift to the reactants and products will decrease

if temp decreases: will shift to the products and reactants will decrease

heat + 2A (g) +B(aq) +6C(s) = 3D(g) +2E (aq)

If temp increases: will shift to the products and reactants will decrease

if temp decreases: will shift to the reactants and products will decrease

Arrhenius definition of acid

produces H+ in solution

Arrhenius definition of base

produces OH- in solution

brosted lowry definition of acid

H+ donor

brosted lowry definition of base

H+ acceptor

arrhenius theory: acids

produce H+ ions in aqueous solution, tends to form hydronium ion (H3O+)

arrhenius theory: bases

produce OH ions in aqueous solution

bronsted lowry theory: acid

H+ donor

bronsted lowry theory: base

H+ acceptor

amphoteric substances

act as either an acid or base (water)

conjugate pairs

base = conjugate acid

acid = conjugate base

Strong Acids

donate all H+ ions and 100% ionized

hydrochloric acid

HCl

hydrobromic acid

HBr

hydriodic acid

HI

Nitric acid

HNO3

perchloric Acid

HClO4

sulfuric acid

H2SO4

weak acids

donate small fraction of their H+ ions, do not donate H+ to water, less than 1% ionized in water

acid ionization constant Ka

larger the Ka stronger the acid

acidic solutions

acidic < 7

basic solutions

basic > 7

pH measuring

pH > 7 is basic and pH < 7 is acidic

pOH measuring

pOH < 7 is basic and pOH > 7 is acidic

relationship of pH and pOH

pH +pOH =14

stronger the acid

smaller the pKa

stronger the base

smaller the pKb

strong basces

more willing to accept H+

weak bases

accepts a small fraction of H+

anions as weak bases

the stronger the acid the weaker the conjugate base

cations as weak acids

the stronger the base the weaker the conjugate acid

strong base + conjugate base of strong acid

neutral solution

strong base and conjugate base of weak acid

basic solution

salt cation

conjugate acid of a weak base

salt cation is the conjugate acid of a weak base, the anion is the conjugate base of a strong acid

acidic solution

salt cation is highly charged metal ion, the anion is the conjugate base of a strong acid

acidic solution

ionization in polyprotic acids

ionize in steps, each H+ has a separate Ka

Strengths of Binary Acids

increasing electronegativity and acidity going to the right.

decreasing bond strength and increasing acidity going down

strengths of oxyacids

acidity decreases down a group

acidity increases to the right across a period

Lewis acid, does not require H+

Lone pair acceptor

Lewis base, does not require H+

Lone pair donor

Buffer

Resists changes in pH by neutralizing added acid or added base

Common ion effect

Weak acid solution, anion NaA, conjugate base of the acid, shifts the position of equilibrium to the left

Buffer capacity

Amount of acid or base a buffer can neutralize

Buffer range

pH range in which the buffer can be effective, an effective range is pKa ± 1

Buffer capacity reaches 1

the ability of the buffer to neutralize both added acid and base improves

titration

a solution of unknown concentration is slowly added to a solution of a known concentration until reaction is complete

equivalence point

moles of acid are equal to the moles of base

strong base added to strong acid

down to up

strong base with a strong acid

up to down

weak acid with a strong base

• before equivalence point, solution becomes a buffer

• beyond equivalence point OH- is in excess

titration of a polyprotic acid

• 2 equibalance points

solubility product (ksp)

equilibrium constant for the dissociation of a solid salt into its aqueous ions

molar solubility

the number of moles of solute that will dissolve in a liter of solution

Ksp and relative solubility

small Ksp is the most insoluble

precipitation

will occur when the concentrations of the ions exceed the solubility of the ionic compound

Q = ksp

solution is saturated no ppt

Q < Ksp

solution is unsaturated no ppt

Q > Ksp

solution above saturation, salt above saturation will ppt

selective precipitation

a solution containing several different cations can often be separated by addition of a regent that will form an insoluble salt with one of the ions but not the others

qualitative analysis

an analytical scheme that utilizes selective precipitation to identify the ions present in a solution

complex ions

ions that form by combining a cation with several anions or neutral molecules

Ligands

ions or molecules that act as lewis bases, H2O

complex ion equilibria

if a ligand is added to a solution that forms a stronger bond than the current ligand, it will replace the current ligand

complex ion formation reaction

the reaction between an ion and ligands to form a complex ion

formation constant (Kf)

• equilibrium constant for the formation reaction

• k’s larger than 1 favors products

solubility of amphoteric metal hydroxides

• many are insoluble

• become more soluble in acidic solution

• some also act as acids, becoming more soluble in basic solution

• cations that form: Al 3+, Cr 3+, Zn 2+, Pb 2+, and Sn 2+