lecture 5

Question 1

alkaline battery

Answer 1

MnO2 -> Mn2O3.+E

ZnO -> Zn -E

balance in basic conditions (with H+ then add OH to both sides, cancel out water)

Question 2

lead acid battery,, car battery,, rechargeable

Answer 2

PbO2 + H2SO4 -> PbSO4 +E
PbSO4 -> Pb + H2SO4 -E

Question 3

lithium cobalt battery,, rechargeable

Answer 3

CoO2 + LiC6 -> LiCoO2 + 6C

Question 4

Fuel Cells,, hydrogen fuel cells

Answer 4

O2 + 2H2 -> 2H2O

Question 5

fuel cells, methanol fuel cells

Answer 5

2CH3OH + 3O2 -> 2CO2 + 4H2O

Question 6

industrial electrolysis : extracting metal from ores

Answer 6

metal extraction requires reduction as metals are usually in their oxidised forms

Question 7

how is iron extracted from ores

Answer 7

using Carbon

produces CO2

Question 8

what can complicate the metal extraction from ores

Answer 8

if the oxide stability is very high

Bauxite (source of Aluminium ) does this

Question 9

how can aluminium be obtained

Answer 9

from aluminium oxide
electrolysed in molten cryolite -960*C

2Al2O3 + 3C -> 4Al + 3CO2

Question 10

how can chlorine be generated

Answer 10

from sodium chloride solution - electrolysis

2H2O + 2Cl- -> Cl2 + H2 + 2OH-

Question 11

what does electrode potential depend on

Answer 11

• ion activity in solution
• potential is affected by a change in pH

Question 12

how can we construct a pH measurement device

Answer 12

vary the pH of solution against a standard electrode

this works bc potential is affected by pH chabges due to it pH being. change in ion activity,, specifically the H+ ion

Question 13

electrochemical cells can be used to determine what

Answer 13

the concentration of ionic species

bc potential is affected by ion activity

Question 14

value of E, G and Q at equilibrium

Answer 14

E and G = 0

Q = K (equilibrium constant)