electrolysis

Question 1

battery of electrolytic cell

Answer 1

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

Question 2

electrolyte of electrolytic cell

Answer 2

-either in solution or molten state
-presence of free mobile ions for flow of electricity

Question 3

electrodes of electrolytic cell

Answer 3

-anode connected to (+) terminal of battery, attracts negatively charged ions/ anions, oxidation occurs
-cathode connected to (-) terminal of battery, attracts positively charged ions/ cations, reduction occurs

Question 4

selective discharge

Answer 4

-selective discharge of cations
-selective discharge of anions
-anion concentration

Question 5

selective discharge of cations

Answer 5

hardest to discharge - potassium
sodium
calcium
magnesium
zinc
iron
lead
hydrogen
copper
easiest to discharge - silver

Question 6

selective discharge of anions

Answer 6

hardest to discharge - sulfate
nitrate
chloride
bromide
iodide
easiest to discharge - hydroxide
half-equation at anode - 4OH-(aq) —> 2H2O(l) + O2(g) + 4e-

Question 7

anion concentration

Answer 7

-the higher the concentration of the anion, the more likely it would be oxidised at the electrode

Question 8

electrolysis using reactive electrodes

Answer 8

-if the anode is a reactive electrode, the anode is oxidised selectively
-electrode at the anode becomes smaller, electrode at the cathode becomes larger

Question 9

electrolytic purification of copper

Answer 9

-the impure copper is the anode and pure copper is used as the cathode
-the electrolyte is an aqueous salt of the metal that is being purified
-impure copper anode dissolves and decreases in mass. impurities from the anode fall to the bottom and a layer of pure copper is deposited at the cathode.

Question 10

electroplating of metal

Answer 10

-the object to be plated is made the cathode while the plating metal is the anode
-the electrolyte is an aqueous salt of the plating metal

Question 11

simple cells

Answer 11

-the anode is the more reactive metal while the cathode is the less reactive metal
-electrons move from the anode to the cathode
-the further apart the metals are in the metal reactivity series, the higher the voltage produced by the simple cell

Question 12

hydrogen fuel cell

Answer 12

-oxygen obtained via fractional distillation of liquid air
-hydrogen obtained via catalytic cracking of long-chain hydrocarbons from petroleum/ crude oil

advantages
-pollution-free because water is the only product formed
-high efficiency in converting chemical to electrical energy

disadvantages
-high cost because hydrogen needs to be liquefied for transport and storage, platinum used as electrodes
-hydrogen is flammable, so special precautions need to be taken in transport of the gas