exam 5; redox and electrochem Flashcards
electrochemistry
linking chemical reactions to electrical work
Spontaneous electrochemical process
reaction that generates electric current
Non Spontaneous electrochemical process
reaction that is driven by electric current
electrochemistry units: mols of e-
coulombs (1 electron = 1.602 x 10^-19 C)
electrochemistry units: rate
Ampere (A) = C/sec
electrochemistry units: gibbs free energy/ energy
volts (V)= J/C
reduction
gain of e- density
oxidation
loss of e- density
oxidation numbers
the charge an atom would have if all of its bonds were perfectly ionic (e- density to more electronegative atom)
Oxidation # rules: elemental atom
Oxidation # = 0
Oxidation # rules: F
Oxidation # = -1 always (most electroneg. atom)
Oxidation # rules: H
H + metal= -1
H + nonmetal= +1
steps to balance redox reactions
1) separate into ox and red half reactions
2)balance half reactions *
3) balance e- reacted/ absorbed
4)recombine half reactions
5) convert to basic conditions if needed (OH-)
6) CHECK: all atoms, e- and charges are balanced
balancing half reactions: balancing non O or H elements
adjust stoich coef
balancing half reactions: balancing O
add H20 to other side of rxn
balancing half reactions: balancing H
add H+ to other side of rxn
balancing half reactions: balancing charge
add e-
voltaic cell
converts the transfer of e-; physically separates 2 half rxn
electrodes: anode
where oxidation takes place (electrons released); - charge
electrodes: cathode
where reduction takes place; e- accepted; + charge
electrodes: inert electrode
electrode that does not participate in rxn (ex. platinum)
salt bridge
closes the circuit to prevent charge build up in half cell; sustain e- flow
