electrolysis

Question 1

what is meant by electrolysis

Answer 1

the breakdown of substances (electrolyte) using electricity

Question 2

why are the electrodes usually inert/ unreactive

Answer 2

so they dont react w the elctrolysis product or the electrolyte

Question 3

why can ionic compounds only be electrolysed when theyre molten or dissolved in water

Answer 3

cause their ions are free to move around and carry diff chargers to the eletrode

Question 4

whats the charge of an anode

Answer 4

positive electrode

Question 5

whats an cathode

Answer 5

negative electrode

Question 6

what happens at the cathode

Answer 6

positively charged ions gain electrons to become stable elements

Question 7

what happens at the anode

Answer 7

negitvely charged ions loose electrons to become stable elements

Question 8

how can reactions at the electrodes be represented

Answer 8

half equations

Question 9

what happens in electolysis of aqeous solutions

Answer 9

in cathode-less reactuve element (metal or hydrogen) is displaced and the more reactive one is left in the solution
in anode- hydroxide ions are discharged unless a halide ion is pressent

Question 10

whatre the steps of extracying aluminium

Answer 10

baxuxite is purified -> aluminium oxide is electrolysed to form aluminium and oxygen

Question 11

whatre the steps to electrolyse aluminium oxide

Answer 11

1- molten aluminium oxide is mixed with cryolite to lower its melting point so less energy is needed
2- carbon electrodes need to be regularly replaced or they burn away
3-aluminium is formed in the cathode and oxygen formed in anode

Question 12

what happens in the anode and cathode in the elctrolysis of aluminium oxide

Answer 12

cathode- aluminium is reduced (gains 3 electrons)
to form Al atoms
anode- oxygen is oxidised (loses 2 electrons) then reacts with the carbon anode to form carbon dioxide gas

Question 13

What is the name of the substance that is mixed with aluminium oxide to lower its melting point?

Answer 13

cryolite

Question 14

whatre the 3 products you get from electrolysising concentrated sodium chloride (brine)

Answer 14

sodium hydroxide,chlorine and hydrogen

Question 15

what happens in the anode cathode and rest of solution in brine

Answer 15

anode- chlorine is oxidised (loses an electron)
cathode- hydrogen displaces sodium and is reduced to (gains 2 electrons)
sodium and hydroxide ions left in the solution react to form sodium hydroxide

Question 16

whatre the uses of hydrogen,chlorine and sodium hydroxide

Answer 16

hydrogen can be used to make margirine
sodium hydroxide used to make paper and bleach and soap
chlorine used to make bleack to disinfect bacteria and plastics

Question 17

where are metals usually formed

Answer 17

at the cathode

Question 18

whats meant by electroplating

Answer 18

coating an object with a metal layer by electrolysis

Question 19

why do we electroplate

Answer 19

• to protect metal from scratches nd corroding
• to preserve and use less amts of expensive and rare metals
• to increase attractiveness

Question 20

how do we electroplate

Answer 20

• use plated object at cathode
  -use plating metal as anode
  -use ions of plating metal in electrolyte

Question 21

what happens when you electolyse copper sulfate

Answer 21

-the cathode gains mass (metals formed) and the anode loses the same mass the cathode gains

Question 22

loss of mass in anode when using active electrode =..

Answer 22

gain of mass in cathode

Question 23

what happens when carbon electrodes are used in copper sulfate

Answer 23

copper is still deposited at cathode
oxygen is given off in anode from the hydroxide ions in electolyte