Ch 18 Electrochemistry Flashcards
Oxidation
Increases oxi #
loses e-s
Oxidation numbers…
Add up to overall charge
Groups 1,2,3 have what oxi number
+1, +2, +3 usually
F is what oxidation number
-1
Cl, Br, and I are what oxi number
Usually -1. Except with O or F (then those overrate)
H is usually what oxi number
+1 except with a metal. Then H is -1
O is what oxidation number usually
-2 except with F where F dominates and Peroxides (-1)
Balancing redox reactions
- Identify oxi and reduction
- Perform material balance(except H and O)
- balance O using H2O
- balance H using H+
- balance Charge
- equalize Electrons
- Add half rxns
Balancing redox rxns in basic soln
- Same as acid except when you add H+ to balance H
You add equal number of OH- to both sides - H+ + OH- = H2O
Anode
Oxidation ( first part in cell diagram)
Cathode
Reduction (last part in cell diagram)
Voltaic / galvanic cell
G
Electrolytic cell
G>0
E
Spontaneous
E>0
G
Equilibrium
Ecell=0
Q=K
Ka equilibrium
Ha+H2O= H3O+ + A-
Kb equilibrium
B + H2O = BH+ + OH-
Ksp
MaXb(s) = aM+ + bX-
Two half cells with same half rxn but different concentrations
Anode is more dilute (lower molarity). E0Cell =0. Ecell>0
Current
Q\T
Amps
C/S
Mol e-
Coulomb/F
Max electrical work of the system
Work = -QE
Max electrical work of surroundings
+QE
Oxidizing agent
Itself is reduced
Reducing agent
Itself is oxidized
Product favored
K>1
Reaction is reversed
G and E change signs
Charge
Current X time
(I x t) = coulombs
Reduction
Reduces #
Gain e-s
S.H.E stands for
Standard hydrogen electrode
2H+ + 2e- = H2
Eo cell = 0
