C6: Electrolysis Flashcards
What is electrolysis
The process of splitting ionic compounds into different elements they are made of. Electrolysis conducts electricity to work.
What does the apparatus contain for electrolysis
Electrodes
Electrolyte
Anode
Cathode
What is an electrolyte
When ionic compounds dissolve in water to make a solution that conducts electricity
What are electrodes
When a voltage (direct current) is applied across the electrolyte, charged ions are attracted to the electrode with with the opposite charge to the ion
What are the two types of electrode and their meaning and charges?
Anode
Cathode
Anions are negatively charged ions and are attracted to the positive electrode (anode)
Cations are positively charged and are attracted to the negative electrode (cathode)
What happens if an ion touches an electrode
Electron transfer, production of elements
How can we use electrolysis to extract metals?
Reactive metals are extracted from molten ores. Electrolysis is used to extract metals like aluminium which are higher in the reactivity series than carbon
What takes place at the anode (positively charged electrode)
Oxygen is formed at the carbon anode. Carbon and oxygen react together to create carbon dioxide. Anode is usually made of carbon as it is a good conductor of electricity and is cheap. This is also where any non metal is formed
What takes place at the cathode (negatively charged electrode)
Aluminium is formed at the cathode. This is also where any metal is formed.
What are the drawbacks of using electrolysis
Lots of energy required to
Produce electric current
Melt the solid ionic compound to allow ion flow
Very expensive
What happens with electrolysis with aqueous solutions
Products of electrolysis of aqueous solutions are unpredictable as water molecules split up to give hydrogen ions and hydroxide ions
What takes place at the cathode (negatively charged electrode)
Hydrogen is produced if the metal is higher than hydrogen in the reactivity series.
The metal is produced if hydrogen is higher than the metal in the reactivity series
What takes place at the anode (positively charged electrode)
What is formed at the anode mainly depends if there are halide ions
If halide ions are present, respective halogen forms
If there are no halide ions, oxygen is formed
What is the half equation at the anode (positively charged electrode)
At the anode, this is where oxidation takes place (loss of electrons and gain of oxygen)
Half equation for bromine
2Br- > Br2 + 2e-
What is the half equation at the cathode ( negatively charged electrode)
At the cathode, this is where reduction takes place (gain of electrons and loss of oxygen)
Half equation for magnesium
Mg2+ + 2e- > Mg
