Chapter 16 - Aqueous Ionic Equilibria

common ion effect

if you add a common ion, the reaction would shift in the direction opposite the ion to achieve equilibrium again

• would change the pH bc the common ion could either increase or lower the production of H+ or OH-

• usually used to “suppress” the ionization or dissociation of a weak acid/base

properties of buffer systems

• contain relatively LARGE amounts of weak acid and their conj base

• ADDED H+ REACTS TO COMPLETION WITH THE WEAK BASE

• ADDED OH- REACTS TO COMPLETION WITH THE WEAK ACID

in buffer systems, the pH is det by

the ratio of the concentrations of the weak acid and weak base.

Maximum buffer capacity

exists when [HA] and [A- ] are LARGE and approximately equal to each other

Buffer range

pH range over which a buffer effectively neutralizes added acids and bases.

Practically, range is 2 pH units around pKa

The closer [HA]/[A-] is to 1, the more effective the buffer.

you can only use the henderson dumb eqn when

you can use initial concentrations of acid and salt.

limits of the henderson eqn

0.1 < [A-]/[HA] < 10

[HA] and [A-] > 100*Ka

equivalence point of titration

the number of moles of OH- added equals the number of moles of H3O+ present!!!!!!!!!!!!!!!!!!!!!!!!

at half equivalent point, the pH

= pKa

titration problems step

1. DO THE STOICHIOMETRY FIRST BITCH WITH NEUTRALIZATION and the concentrations not the moles

2. do equilibrium with the “final” concentrations

solubility prod constant

Qsp = [M]^q[X]^p

when equilibirum is estalished in solubility dumb shit,

no more of the salt dissolves and the soln is saturated

molar solubility or solubility

the x term in equil or the equil concen of the ion that has a coeff of 1 in the chem eqn

• use stoichiometry to get the equil concens of the other ions

to figure out which salt precipitates first

• note the common ion between them

• The substance whose Ksp is first exceeded precipitates first.

• The ion requiring the LESSER amount of the common precipitates first.

in simultaneous equilibria

• you must find the NET REACTION and Knet

• so reverse reactions and shit and fucking add the dumb stuff together

• the eqn with the higher Ksp is NOT reversed

to find ho wmuch remains of something after something has ifrst precipitates

ue the Ksp bro…