C6 - Electrolysis Flashcards
What are Ionic Equations
Equations that only show the atoms and ions that change in a reaction
What is the definition of electrolysis
The splitting up of compounds using electricity
How do you set up a circuit for electrolysis
Dip two electrodes in the electrolyte with a gap in between, connected to a power supply
What is the positive electrode called
Anode
What is the negative electrons called
Cathode
What are the electrodes made of
Unreactive (inert) substances, such as graphite, so they don’t react with the electrolyte or the products
What moves to the anode and what moves to the cathode
Negatively charged ions (non-metals) move to the anode and positively charged ions (metals) move to the cathode
What happens at the anode
Oxidation as negative ions lose electrons to become neutral atoms
What happens at the cathode
Reduction as positively charged ions gain electrons to become neutral atoms
Why are 4 ions present in aqueous solutions
There are 2 ions present from the compound and H+ and OH- ions present from the water
What are the rules of aqueous solutions at the anode
If the -Ions are halogens then the halogen is produced (discharged). If the -Ions are not halogens then oxygen is produced (discharged from hydroxide ions)
What are the rules for aqueous solutions at the cathode?
If the +ions are more reactive than hydrogen then hydrogen is produced (metal displaces into solution). If the +ions are less reactive that hydrogen then the metal is produced
What is aluminium oxide mixed with for electrolysis and why?
Aluminium oxide is mixed with molten cryolite to lower the melting point to reduce costs for electrolysis
What happens at the anode during the electrolysis of Aluminium oxide
Negative O2 ions are attracted to the anode where they each lose 2 electrons and then combine to form neutral O2 molecules and are produced as oxygen gas
What happens at the cathode during the electrolysis of Aluminium Oxide
Positive aluminium 3+ ions are attracted to the cathode where they reduce to gain 3 electrons and form neutral aluminium atoms which sink to the bottom of the electrolysis cell and are collected from the cell
What happens to the oxygen because of the carbon rods
The oxygen produced reacts with the hot ion electrodes to produce carbon dioxide gas and this means that the carbon anodes burn away and need to be replaced regularly
What ions are present in the electrolysis of Sodium Chloride
Na+, Cl- , OH- , H+
What happens at the cathode during the electrolysis of sodium chloride
Sodium and Hydrogen positive ions are attracted to the cathode. Sodium metal is more reactive than hydrogen so displaces it in the solution and hydrogen gas is produced (discharged)
What happens at the anode during the electrolysis of Sodium Chloride
Chloride and Hydroxide ions are attracted to the anode. Chloride is discharged as it is a halogen which produces bubbles of pale green gas and OH- is left in the solution
What are the end products of the electrolysis of Sodium Chloride and their uses
- Chlorine - used to disinfect swimming pools and make PVC
- Hydrogen - used as a fuel and in making margarine
- Sodium Hydroxide - used to make soap and other chemicals
How do you test for chlorine gas?
Chlorine bleached damp litmus paper, turning it white
How do you test for Hydrogen gas
Hydrogen gas makes a ‘squeaky pop’ with a lighted splint
How do you test of oxygen
Oxygen gas will relight a glowing splint
