Electrochemistry

Question 1

Define electrolysis

Answer 1

Electrolysis is the process of using electricity to break down or decompose a compound.
During this process, electrical energy is converted to chemical energy.
It has an important use in the extraction of useful elements from compounds. [Very stable metal compounds]

Question 2

ANOCAR

Answer 2

Anode Oxidation
Cathode Reduction

Question 3

ELECTROLYTIC CELL
electron supplier to which electrode

Answer 3

(-) terminal of BATTERY to cathode

Question 4

ELECTROLYTIC CELL
electron receiver from which electrode

Answer 4

(+) terminal of BATTERY from anode

Question 5

Simple Cell

Answer 5

Anode:
- Source of es (Supplier)
- More reactive, higher up in reactivity series
- Greater tendency to lose es, more readily oxidised

Cathode:
- Rich in es (Reciever)

Process:
- Electrons move from anode to cathode thru wire
- Spontaneous redox rxn. generates electrical energy measured using voltmeter

Question 6

attracts positively charged ions

ANOCAR

Answer 6

cathode

Question 7

attracts negatively charged ions

ANOCAR

Answer 7

anode

Question 8

reduction occurs

anocar

Answer 8

cathode

cathode -> positive ions become neutral -> gain es -> reduction

Question 9

oxidation occurs

anocar

Answer 9

anode

anode -> negative ions become neutral -> lose es -> oxidation

Question 10

battery (3)

Answer 10

• provide electrical energy to drive the chemical reaction
• (+) terminal receives electrons from anode
• (-) terminal supplies electrons to cathode

Question 11

electrolyte

Answer 11

• molten (l) or aqueous (aq) state
• presence of free mobile ions to allow flow of electricity

Question 12

auto ionisation of water

Answer 12

h2o (l) <-> h+ (aq) + oh- (aq)
h+ (aq) + 2e- -> h2 (g)
4oh- (aq) -> 2h2o (l) + o2 (g) +4e-

Question 13

cations ease of discharge

reactivity series

Answer 13

Potassium+
Sodium+
Calcium2+
Magnesium2+
Aluminium3+
Carbon4+
Zinc2+
Iron2+
Lead2+
Hydrogen+
Copper2+
Silver+
Gold+

Question 14

anions ease of discharge

Answer 14

F^-
So4^2-
NO3^-
Cl^-
Br^-
I^-
OH^-

Question 15

what anions arent discharged even if in high conc

Answer 15

f-, so4 2-, no3 - bc of very low tendency to be oxidised

Question 16

inert electrodes

Answer 16

graphite n platinium
paladium rarely use bc expensive

Question 17

Half ionic eqns for cations

(aq) -> (s) except hydrogen (g)

Answer 17

Potassium+
(K⁺) + e⁻ → K (s)

Sodium+
(Na⁺) + e⁻ → Na (s)

Calcium2+
(Ca²⁺) + 2e⁻ → Ca (s)

Magnesium2+
(Mg²⁺) + 2e⁻ → Mg (s)

Zinc2+
(Zn²⁺) + 2e⁻ → Zn (s)

Iron2+
(Fe²⁺) + 2e⁻ → Fe (s)

Lead2+
(Pb²⁺) + 2e⁻ → Pb (s)

Hydrogen+
(H⁺) - 2H⁺ + 2e⁻ → H₂ (g)

Copper2+
(Cu²⁺) + 2e⁻ → Cu (s)

Silver+
(Ag⁺) + e⁻ → Ag (s)

potassium, sodium, hydrogen, silver

Question 18

Half ionic eqns for anions

Answer 18

1. (F^-): 2F^- → F2 + 2e-
2. (SO4^2-): 4SO_4^2- → 2S2O8^2- + 4e-
3. (NO3^-): 4NO_3^- → 2NO2 + O2 + 4e-
4. (Cl^-): 2Cl^- → Cl2 + 2e-
5. (Br^-): 2Br^- → Br2 + 2e-
6. (I^-): 2I^- → I2 + 2e-
7. (OH^-): 4OH^- → O2 + 2H2O + 4e-

Question 19

Selectively Discharged
VS
Selectively Oxidised

Answer 19

Discharged:
1. For ions w/ charges
2. Lose charge from + to neutral

Oxidised:
1. For metal electrodes (w/ no charges)
2. Gain charge from neutral to +