Electrical Conductivity + Electrolysis (1) Flashcards
Electrical conductivity is all about the movement of electrons or _______
Ions
Electrons have a negative charge. What about ions?
They can have either positive or negative
_____________ or ______ can act as charge carriers - they can move charge around a system to create a flow of ________________
Electrons
Ions
Electricity
The electric current is the flow of ___________ or _______
Electrons or ions
Ionic compounds are made of a lattice of positive and negative ______
Ions
Why don’t solid ionic compounds conduct electricity
Because the ions aren’t free to move around
Can ionic compounds conduct electricity…
When molten or in solution
Why can an ionic compound conduct electricity when dissolved or molten
The ions separate and are free to move around in the solution. This means that they’ll carry electric current and so conduct electricity.
Can covalent compounds conduct electricity
No (except graphite)
Why can’t covalent compounds conduct elctricity
They don’t contain ions because they make bonds by sharing electrons. This means that they don’t have any charge carriers that are free to move - so they can’t carry an electric current
Metals are held together by ____________ bonding
Metallic
Metals have giant structures of ______________ ions surrounded by a sea of delocalised (free) ____________
Positive ions surrounded by a sea of delocalised (free) electrons
The attraction between positive ions and the delocalised electrons is called _____________ bonding. It’s this ______________ bonding which gives metals their ______________
Metallic
Metallic
Properties
Metals are good conductors of electricity and heat. Why?
Because the delocalised electrons carry electrical current and heat energy through the material.
The layers of atoms in a metal can slide over each other, making materials _______________ - this means that they can be hammered or rolled into flat sheets
Malleable
What is electrolysis
The decomposition of an ionic substance using electricity
What is an anode
The positive electrode
What is a cathode
The negative electrode
Cations are ________________ ions which are attracted to the _________________ electrode (also known as the ____________). They __________ electrons and are _____________
Positive Negative Cathode Gain Reduced
Anions are ________________ ions which are attracted to the _________________ electrode (also known as the ____________). They __________ electrons and are _____________
Negative Positive Anode Lost Oxidised
If you pass an electric current through an __________ substance that’s molten or in solution it breaks down into new ______________. This is called ________________
Ionic
Substances
Electrolysis
Electrolysis requires a liquid to conduct the electricity, called the _____________
Electrolyte
How are electrolytes made?
By melting or dissolving ionic compounds
How does an electrolyte conduct electricity
Via the free ions
For the circuit to be complete, there’s got to be a flow of _____________. Electrons are taken away from ions at the ____________ and given to the other ions at the _____________
Electrons
Anode
Cathode
As ions gain or lose electrons they become _________ or ____________
Atoms
Molecules
What are electrolytes
Liquids that conduct electricity
Why can’t a covalent compound conduct electricity
Because they have no free electrons and no ions
One way to distinguish between electrolytes and non-electrolytes. When you place a conductivity probe in an ______________, current flows through the circuit - so you can measure its ______________. What happens if you place it in a non-electrolyte?
Electrolyte
Conductivity
You get a reading of 0 conductivity - no flow
Molten ionic _____________ can be _____________ easily because the ions can move freely. They’re usually broken up into their ____________.
Compounds
Electrolysed
Elements
Common example of electrolysis:
Molten lead bromide
Pb2+ + 2e- –>
Pb
2Br- —>
Br2 + 2e-
What is the difference with electrolysis of aqueous solutions
There will be hydrogen ions and hydroxide ions from the water
Aqueous electrolysis:
At the cathode, what happens if H+ ions and metal ions which are more reactive than them are present
Hydrogen gas will be produced if the metal ions are more reactive than the H+ ions.
Aqueous electrolysis:
At the cathode, what happens if H+ ions and metal ions which are less reactive than them are present
A solid layer of the pure metal will be produced
What happens at the anode, if OH- and halide ions are present
Molecules of chlorine, bromine or iodine will be formed
What happens at the anode, if OH- and no halide ions are present
Oxygen will be formed
How can you increase the number electrons transferred
Time - (electrolysing for a longer time)
Current - increasing
What does the amount of product made by electrolysis depend on
The number of electrons that are transferred
At the negative electrode:
Metal ions and hydrogen ions are positively charged. Whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series.
If the metal is more reactive than hydrogen which will be produced?
Hydrogen
Which will be produced if the metal is less reactive than hydrogen?
The metal
What is brine
Concentrated sodium chloride solution
What happens if brine is electrolysed
Hydrogen gas forms at the negative electrode
Chlorine gas forms at the positive electrode
Also a solution of sodium hydroxide forms
