Electrolysis Flashcards
Describe a metal in terms of electrons?
A giant structure of positive ions surrounded by a sea of delocalised electrons
What is the attraction between positive and negative ions called?
Metallic bonding
Why are metals good conductors of electricity and
heat?
The delocalised electrons can move through the material
Why are most metals malleable?
The layers of atoms in a metal can slide over each
other
What is an electric current?
A flow of electrons or ions
Why don’t covalent compounds conduct electricity?
They don’t contain ions so they don’t have any charge carriers that are free to move (excludes graphite)
Why do ionic compounds only conduct electricity when molten or in solution?
Solid ionic compounds don’t conduct because ions aren’t free to move. When a compound is dissolved, the ions separate and are free to move in the solution
What does electrolysis involve?
The formation of new substances when ionic compounds conduct electricity
How can you distinguish between an electrolyte and a non-electrolyte?
When you place a conductivity probe in an electrolyte, current flows through the circuit - so you can measure its conductivity. No current flows through a non electrolyte
Describe an experiment to investigate electrolysis?
Molten ionic compound can be electrolysed because the ions can move freely. They’re usually broken up into their elements. A good example is molten lead bromide (PbBr2).
> +ve Pb2+ ions are attracted to the -ve cathode
> -ve Br- ions are attracted to the +ve anode
What happens at the cathode?
The positive ions are attracted to the negative cathode where they accept electrons and become an atom. The atoms sink to the bottom
What happens at the anode?
The negative ions are attracted to the positive anode where they lose electrons and become an atom. The atoms form at the top of the anode
What is the half equation for the reaction at the cathode for molten lead bromide?
Pb2+ + 2e- –> Pb
What is the half equation for the reaction at the anode for molten lead bromide?
2Br- –> Br2 + 2e-
What is the relationship between faradays and moles of electrons?
One farady represents one mole of electrons
