Electrochemical cells Flashcards
what are electrochemical cells made from?
-two different metals dipped in salt solutions of their own ions
what is a salt bridge used for?
-completes circuit
-allows ions to flow
which way do electrons flow?
from most reactive metal to least reactive
what is the order of a conventional representation?
-oxidation on the left
-reduction on the right
which electrodes does reduction / oxidation occur at?
reduction - positive
oxidation - negative
is oxidation a more negative or positive number?
more negative
how do you calculate cell potential?
E(RHS) - E(LHS)
E(Reduced) - E(Oxidised)
what are the standard conditions?
1.00moldm-3
298K
100kPa
describe a standard electrode
-hydrogen gas bubbled through H+ solution
-platinum electrode
in a standard electrode, what is the H+ solution and concentration?
-HCl
-1.00moldm-3
in a table of values, what is the strongest reducing agent?
-most negative value
in a table of values, what is the strongest oxidising agent?
-most positive value
what are two examples of non-rechargeable cells
-zinc-carbon
-lithium-manganese
what are half equations for a zinc-carbon cell?
zinc : Zn(s) –> Zn2+(aq) + 2e-
carbon : 2NH4+ (aq) + 2e- –> 2NH3(g) + H2(g)
overall : 2NH4+(aq) + Zn(s) –> 2NH3(g) + H2(g)+ Zn2+(aq)
what are half equations of a lithium-manganese dioxide cell?
Li+(aq) + e- –> Li(s)
Li+(aq) + MnO2(s) + e- –> LiMnO2(s0
overall : Li + MnO2 –> LiMnO2
what are examples of rechargeable batteries?
-lead-acid
-nickel-cadmium
-lithium ion
what are half equations for a lead-acid cell
lead plate :
Pb(s) + SO42-(aq) –> PbSO4(s) + 2e-
lead-dioxide plate :
PbO2(s) + 4H+(aq) +SO42-(aq) + 2e- –> PbSO4(s) + 2H2O(l)
overall :
PbO2(s) + 4H+(aq) + 2SO42-(aq) + Pb(s) –> 2PbSO4(s) + 2H2O(l)
what are equations for a nickel-cadmium cell
Cd(OH)2(s) + 2e- –> Cd(s) +2OH-(aq)
NiO(OH)(s) + H2O(l) + e- –> Ni(OH)2(s) + OH- (aq)
2NiO(OH)(s) + Cd(s) + 2H2O(l) –> 2Ni(OH)2(s) + Cd(OH)2(s)
