1.54 describe experiments to investigate electrolysis, using inert electrodes, of aqueous solutions such as sodium chloride, copper(II) sulphate and dilute sulphuric acid and predict the products

In aqueous solutions, as well as ions from the ionic compound, there will be hydrogen ions (H+) and hydroxide ions (OH-) from the water.

Products

At the cathode, if H+ ions and metal ions are present, hydrogen gas will be produced if the metal ions are more reactive than H+ ions (for example, sodium ions). If the metal ions are less reactive than the H+ ions (for example, copper ions), a solid layer of the pure metal will be produced.

At the anode, if OH- and halide ions (Cl-, Br-, I-) are present, then molecules of chlorine, bromine or iodine will be formed. If no halide ions are present, then oxygen gas and water will be formed.

Electrolysis of sulphuric acid
A solution of sulphuric acid (H2SO4) contains three different ions: SO₄²⁻ , H+ and OH-.

At the cathode: as sulphur (SO₄²⁻) is more reactive than hydrogen, hydrogen gas is produced...

2H+ + 2e- ---> H2


At the anode: as there no halide ions present, oxygen and water is produced.

4OH- ---> O2 + 2H2O + 4e-


Electrolysis of sodium chloride
A solution of sodium chloride (NaCl) contains four different ions: Na+, Cl-, OH- and H+

At the cathode: as sodium is more reactive than hydrogen, hydrogen gas is produced...

2H+ + 2e- ---> H2

At the anode: as chlorine ions are present (halide), then chlorine atoms will be produced (as chlorine gas)...

2Cl- ---> Cl2 + 2e-


Electrolysis of copper(II) sulfate
A solution of copper(II) sulphate (CuSO4) contains four different ions: Cu2+, SO₄²⁻, H+ and OH-.

At the cathode: as copper is less reactive than hydrogen, copper metal is produced...

Cu2+ + 2e- ---> Cu

At the anode: as there are no halide ions present, oxygen and water are produced...

4OH- ---> O2 + 2H2O + 4e-

1.53 describe experiments to investigate electrolysis, using inert electrodes, of molten salts such as lead(II) bromide and predict the products.

Firstly, inert electrodes are just ones that don't react easily (like at all).

NOTE: The cathode (negative) attracts Pb2+ ions as they are positive, the anode (positive) attracts Br- ions as they are negative

- As soon as the lead(II) Bromide melts(becomes molten), the ions become free to move around, this movement enables the ions move allowing a charge to flow, meaning electrolysis can take place. 

- The electrodes are made out of carbon - which is inert (unreactive). 

- Connect the electrodes to a power source

- The positive lead (II) ions are attracted to the cathode, which is the negative electrode. When they get there, they gain 2 electrons each from the electrode. This forms lead atoms (they are no longer ions as they have no charge). These 'fall' to the bottom of the container as molten lead. 

- Bromide ions (negative) are attracted to the positive anode. When they get there, the extra electron which makes the bromide ion negatively charged moves onto the anode, this loss of the extra electron turns each bromide ion into a bromine atom. These join in pairs (bond covalently) to form bromine molecules (which is gas). 

The half equations...

At the cathode: Pb2+ + 2e- ---->  Pb

At the anode: 2Br^- ---> Br₂ + 2e^-

1.52 understand that electrolysis involves the formation of new substances when ionic compounds conduct electricity

During electrolysis, ionic compounds conduct electricity (because they are molten so they have free ions). During electrolysis, negative ions (anions) are attracted to the positive electrode (the anode) and positive ions (cations) are attracted to the negative electrode (the cathode). For the circuit to be complete there has to be a flow of electrons. For this to occur, electrons are taken away from negative ions at the anode (positive electrode) and given to positive ions at the cathode (negative electrode). This means that the ions in the electrolyte undergo a reaction whereby they either gain or lose electrons (reduction or oxidation) and so a new product is formed at each electrode (because as ions lose electrons, they become atoms or molecules).

1.51 describe experiments to distinguish between electrolytes and non-electrolytes

When you place a conductivity probe in an electrolyte, current will flow through the circuit - this means you can measure its conductivity.

When you place conductivity probe in a non-electrolyte, no current will flow - this means you will get a reading of 0 conductivity

Another way to determine whether a substance is an electrolyte or non-electrolyte is to set up an electrolytic cell - if the substance will undergo electrolysis then it is an electrolyte, if not, it is not.

1.50 understand why ionic compound conduct electricity only when molten or in solution

Electrolysis requires an electrolyte (a liquid that an conduct electricity), electrolytes are made by melting or dissolving ionic compounds, this results in free ions which conduct electricity. Molten ionic compounds can conduct electricity because the ions can move freely.

1.49 understand why covalent compounds do not conduct electricity

In a covalent compound, there are no delocalised electrons, so it cannot hold a current (in other words, there are no electrons free to move, therefore there can be no transfer of electricity). 

NOTE: Graphite is an exception as this is a giant covalent structure and has the 4th ion free to move, so graphite can conduct electricity

1.48 understand that an electric current is a flow of electrons or ions

An electric current is a flow of electrons, it an also be a flow of ions (as the are charged). Its basically a flow of charged particles.