Required Practical - Electrolysis Flashcards
What is the point of the experiment?
To find out how different solutions behave when electrolysed
What is electrolysis?
the use of an electrical current to break down compounds containing ions into their constituent elements
What is an electrolyte
the substance being broken down
What are electrodes made of?
solids that conduct electricity
What is the anode?
the positive electrode where negatively charged ions move to
What is the cathode?
the negative electrode where positive ions move to
Example of lead Bromide:
- The lead bromide is heated until it has melted
- The positively charged lead ions move to the negative cathode
- Here they gain electrons to form lead atoms - pure lead produced at this electrode
- The negatively charged Bromide ions move to the positive anode
- Here they lose electrons to form bromine atoms, which join together to form bromine molecules - bromine is released at this electrode
Cathode - Pb(2+) + 2e- –> Pb
Anode - 2Br- –> Br2 + 2e-
Ionic substances can only conduct electricity when they are:
molten or dissolved in water
What is Oxidation?
loss of electrons
When does oxidation occur?
when negatively charged ions lose electrons at the positive electrode.
What is reduction?
gain of electrons
When does reduction occur?
when positively charged ions gain electrons at the negative electrode
What is the reaction called when both oxidation and reduction occur?
A redox reaction
Why must Electrodes be inert?
so they don’t react with the electrolyte or the products.
Why does a metal hydroxide sometimes get produced?
Because if the metal is more reactive than hydrogen then hydrogen s produced at the negative electrode instead of the metal.
Method:
- set up equipment
- pass an electric current through the aqueous solution
- observe the products formed at each inert electrode
How would you test for the gas?
Hydrogen - pop due to the lit splint
Chlorine - bleaches damp litmus paper
What would happen if you added the universal indicator to the solution?
It would turn purple as a production of hydroxide is an alkali
Hazards:
- a low voltage must be used to prevent electrocution
- the room must be well ventilated due to the production and exposure to the harmful chlorine gas
What is the anode made of when electrolysis is used for extraction?
Carbon
