chem 2 exam #1

henry’s law

S=k_HP

• solubility = henry’s law constant x partial pressure

solubility for gases + solids

gases: less soluble at higher temperatures (moving faster)

solids: more soluble at higher temperatures (melts)

molality

m = (mole of solute/kg of solvent)

molarity

M = (mole of solute / L of solution)

benzene

C₆H₆

osmotic pressure equation

π = iMRT

• π = osmotic pressure (atm)

• i = van’t hoff factor

• M = molar concentration of solute (mol/L)

• R = ideal gas constant (0.0821 L atm / mol K)

• T = temperature (K)

freezing point depression

change in T = i m K_f

at equilbrium…

1. concentrations of reactants and products remain constant over time

2. rate of forward and reverse reactions are equal

3. reactants are being converted to products and vice versa

K constant

aA + bB ←→ cC + dD

K_p=([C]^c[D]^d) / ([A]^a[B]^b)

K>1

product favored

K<1

reactant favored

K vs Q

• K is a constant and known; only changes with temperature

• Q is unknown and must be found; changes with concentration/pressure and temperature

K < Q

• favored in reverse to reactants

K > Q

• favored in forward direction to products

moves to products when (temp, K, Q)

temp increases: +, Q < K, K increases

temp decreases: -, Q < K, K increases

moves to reactants when (temp, K, Q)

temp increases: -, Q > K, K decreases

temp decreases: +, Q > K, K decreases

Lewis

acid: accepts electron pair

base: donates electron pair

bronsted lowry

is a lewis

acid: proton donor

base: proton acceptor

arrhenius

lewis and bronsted lowry

acid: H+ in H2O

base: OH- in H2O

amphoteric

• has both, can act as an acid or a base

• HCO₃^-, HSO₄^-, H₂O

examples of lewis acids

non-metal oxides

CO₂, SO₂, N₂O₅, NO

carbonic acid

H₂CO_{3 (aq)}

hydrogen carbonate

HCO₃^-

hydronium ion

H₃O⁺_(aq)

strong ionic bases

• 100% ionized, completely dissociates to form OH^-

• oxides and hydroxides of alkali metals, Ca, Sr, Ba

strong acids

• ionize completely in water

• CB don’t react with water

weak acids

• ionize partially in water

• CA are weak and partially react with water

strong acids

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

what does pKa/b/Ka/b say about acid/base strength

high Ka = small pKa = stronger acid

high Kb = small pKb = stronger base

pH, pOH, [H₃O⁺], [OH^-], pK_w, etc equations

pH = -log[H₃O]

pOH = -log[OH^-]

[H₃O⁺] = 10^-pH

[OH^-] = 10^-pOH

pK_w = -log(Ka)

pH + pOH = 14

pKa + pKb = 14 (CB/A pair)

oxoacids

greater # of EN O atoms → stronger acid

bond strength vs acid strength

strength of bond decreases → strength of acid increases

acids

bonds with nonmetals

bases

bonds with metals

amphoteric

sitting near metalloid line (higher oxidation rate)