Electrochemical cells

Question 1

what are electrochemical cells made from?

Answer 1

-two different metals dipped in salt solutions of their own ions

Question 2

what is a salt bridge used for?

Answer 2

-completes circuit
-allows ions to flow

Question 3

which way do electrons flow?

Answer 3

from most reactive metal to least reactive

Question 4

what is the order of a conventional representation?

Answer 4

-oxidation on the left
-reduction on the right

Question 5

which electrodes does reduction / oxidation occur at?

Answer 5

reduction - positive
oxidation - negative

Question 6

is oxidation a more negative or positive number?

Answer 6

more negative

Question 7

how do you calculate cell potential?

Answer 7

E(RHS) - E(LHS)
E(Reduced) - E(Oxidised)

Question 8

what are the standard conditions?

Answer 8

1.00moldm-3
298K
100kPa

Question 9

describe a standard electrode

Answer 9

-hydrogen gas bubbled through H+ solution
-platinum electrode

Question 10

in a standard electrode, what is the H+ solution and concentration?

Answer 10

-HCl
-1.00moldm-3

Question 11

in a table of values, what is the strongest reducing agent?

Answer 11

-most negative value

Question 12

in a table of values, what is the strongest oxidising agent?

Answer 12

-most positive value

Question 13

what are two examples of non-rechargeable cells

Answer 13

-zinc-carbon
-lithium-manganese

Question 14

what are half equations for a zinc-carbon cell?

Answer 14

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)

Question 15

what are half equations of a lithium-manganese dioxide cell?

Answer 15

Li+(aq) + e- –> Li(s)
Li+(aq) + MnO2(s) + e- –> LiMnO2(s0
overall : Li + MnO2 –> LiMnO2

Question 16

what are examples of rechargeable batteries?

Answer 16

-lead-acid
-nickel-cadmium
-lithium ion

Question 17

what are half equations for a lead-acid cell

Answer 17

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)

Question 18

what are equations for a nickel-cadmium cell

Answer 18

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)