Chem 260 Exam #2

what are the conditions in which the small x approximation can be made

if the change is small (less than 5%) compared to the initial concentration

what will happen to a system if it experiences perturbation when it was initially at equilibrium

it will shift to counteract the effect of the perturbation

endothermic reaction

A reaction in which energy/heat is absorbed

what side of the reaction is heat consumed in an endothermic reaction

left/reactants

what side of the reaction is heat released in an exothermic reaction

right/products

exothermic reaction

A reaction that releases energy in the form of heat

acid

proton donor

base

proton acceptor

Kb

base dissociation constant

Ka

acid dissociation constant

Autoionization of Water constant

Kw = 1.0x10-14

equilibrium expression for Kw

Kw = [H3O+][OH-]

HCl

strong acid

HBr

strong acid

HI

strong acid

HNO3

strong acid

H2SO4

strong acid

HClO3

strong acid

HClO4

strong acid

LiOH

strong base

NaOH

strong base

KOH

strong base

Ca(OH)2

strong base

Ba(OH)2

strong base

Sr(OH)2

strong base

for strong acids, what is [acid] equal to

[H3O+]

for strong bases what is [base] equal to

[OH-] = n x [base]

strong acid

HA molecules completely dissociate

weak acid

HA molecules partially dissociate

for weak acids what is [H3O+] equal to

square root of Ka x [acid]

for weak bases what is [OH-] equal to

square root of Kb x [base]

examples of weak acids

NH4+, H2PO4, HF, HSO4-, CH3COOH

examples of weak bases

NH3, HPO4, F-, SO4-, CH3COO-

if [acid] = [base]

pH = pKa

if [acid] > [base]

pH < pKa

if [acid] < [base]

pH > pKa

buffer capacity

the amount of added acid or base 1L of a buffer can neutralize before the buffer is destoroyed

what does buffer capacity depend on

absolute concentrations; not just ratios

buffer solutions resist a . . .

change in pH

equivalence point

the point at which the two solutions used in a titration are present in chemically equivalent amounts

half equivalence point

The point in a titration at which exactly half the molar equivalence of reactant is consumed by the titrant being added. At this point in an acid-base titration, the pKa of the unknown solution is revealed.