C6 (Electrolysis) Flashcards
Electrolysis Definition
Decomposition of ionic substances by passing an electrical current through them
What occurs at the positive electrode (Anode)
- Oxidation (looses electrons)
- anions (negative ions) move to it
What occurs at the negative electrode (cathode)
- reduction (gains electrons)
- cations (positive ions) move to it
Why can electrolysis occur on in molten ionic substances
- ionic solid is in fixed positions
- molten ionic as ions move freely and creates a flow of charge
Write a half equation for Br2 at the Anode
2Br(^-) - 2e(^-) -> Br2
Write a half equation for Lead at the Cathode
Pb(^2+) + 2e(^-) -> Pb
Why are metals extracted from ores using electrolysis + 2 disadvantages
This is when the metal is too reactive to be reduced with carbon.
- very expensive + lots of energy
3 steps to how aluminium becomes a molten mixture
1) extracted as bauxite ore, that contains aluminium oxide
2) oxide high melting temp, mixed with cryolite to lower melting temp
3) now molten, free ions to conduct electricity
What is the half equation of O2 at the anode (for aluminium extraction)
20(^2-) - 4e(^-) -> O2
What is the half equation for Al3 at the cathode (for aluminium extraction)
Al(^3+) + 3e(^-) -> Al
What substances are contained in an aqueous solution + equation
H+, OH- , H20
- reversible reaction
H20 H(^+) + OH(^-)
What happens at the cathode if metal ions are more reactive than hydrogen?
Hydrogen gas will be produced
What happens at the cathode if metal ions are less reactive than hydrogen?
A solid layer of pure metal produced
What happens at the anode is there are OH- and halide ions?
Halide molecules will be formed
What happens at the anode if no halide ions are present?
OH- discharged and oxygen formed (as bubbles with water
