chapter 20 + 21 electrochemistry and equilibria

oxidation number of cl

-1 (except when combined with O or F)

ox number of H

-1 in metal hydrides, +1 in everything else

ox number of O

-2 except in peroxides (-1) or OF2 (+2)

balancing redox reactions in acidic/basic solutions

divide the reaction into half reactions

balance the atoms in each half reaction

balance the O by adding H2O

balance the H by adding hydride ions (in acid) or OH (bases)

balance the charges by adding electrons

put the reactions back together and multiply

electrolysis cell

faraday's law

Q = I x t

Q= total charge (coulombs, C)

I= current in Amps (A)

t= time (s)

nerst equation

standard electrode potential

the voltage produced when a standard half cell is connected to a standard hydrogen electrode under standard conditions

standard cell potential

the difference in the standard electrode potential between two specified half cells

conjugate pair

an acid base pair on each side of an acid base neutralisation reaction that are related to each other by the difference of a hydrogen ion

pH

-log[H+]

Kw

ion product constant for water (1.0 x 10^-14)

[H+][OH-]

Ka

acid dissociation constant; high = likely to dissociate (ionize), small = unlikely/less dissociation

buffer solution

a solution that minimizes changes in pH when moderate amounts of an acid or base are added

calculating pH of a buffer solution

pH=pKa+log (conjugate base/weak acid)

Ksp

solubility product constant

common ion effect

a decrease in the solubility of an ionic compound caused by the addition of a common ion

Kpc

partition coefficient

[X(solvent A)]/[X(solvent B)]