C6 Flashcards
What does electrolysis mean?
Splitting up with electricity
What happens during electrolysis?
1) A current is passed through an electrolyte and the ions move towards the electrodes where they react and the compound decomposes.
What do the positive ions move towards and what do they do?
Cathode(- electrode) and gain electrons
What do they negative ions move towards and what do they do?
Anode (+ electrode) and lose electrons
What is the differnece between an electrolyte and electrode?
- Electrolyte is a liquid or solution that conducts electricity
- An electrode is a solid that conducts electricity
After they have oxidised or reduced what happens?
There is a flow of charge through the electrolyte and the ions travel to the electrodes
What happens when an ion gains or loses an electron?
They form an uncharged element and are discharged from the electrolyte
What forms elements?
Electrolysis of molten ionic solids
Why can’t an ionic solid be electrolysed?
The ions are in fixed positions and can’t move
Why can molten ionic compounds be electrolysed?
The ions can move more freely and conduct electricity
What happens at the cathode?
Positive metal ions are reduced
What happens at the anode?
Non metal ions are oxidised
How can metals be extracted from their ores?
By using electrolysis
What happens if an element is more reactive than carbon?
You have to use electrolysis to extract the metal
Why extracting metals expensive?
You need a lot of energy
What is used to lower the melting point?
Cryolite
Why does the positive electrode need to be continually replaced?
Oxygen is formed which reacts with carbon and will make carbon dioxide
What ions are in the water?
H+ and OH-
What happens if H+ ions and metal ions are present?
Hydrogen gas will be produced if the metal ions are more reactive than hydrogen
What happens if the metal ion is less reactive than hydrogen?
A solid layer of the pure metal will be produced
At the anode what happens if OH- and halide ions are formed?
The halide ions will be formed
What are the halide ions?
Cl-,Br-,I-
What happens if no halide ions are formed?
OH- ions are discharged and oxygen will be formed
What is the oxygen equation?
4OH- —> O2 + 2H2O + 4e-
What is the test for chlorine?
Bleaches Damp litmus paper = white
Whats the test for hydrogen?
Squeaky pop with lighted splint
Test for oxygen?
Relight glowing splint
What’s the equipment for electrolysis?
Test tubes.
Electrolyte solutions.
100 cm3 beaker.
Stand and clamp.
Two carbon rod electrodes.
Two crocodile / 4 mm plug leads.
Low voltage power supply.
Blue litmus paper
What’s the method for electrolysis?
1) Set up the apparatus
2) Add the aqueous solution to the beaker
3) Add to graphite rods and connect them to the power supply with the crocodile teeth
4) turn on power supply
5) Record results in a table and repeat for another solution and see if any metal has been formed
6)
What ore is aluminium extracted from?
Bauxite
