Chapter 15: Electrolysis

15.1-Electrolysis

Electrolysis is a promising option for carbon-free hydrogen production from renewable and nuclear resources.
Electrolysis is the process of using electricity to split water into hydrogen and oxygen.
This reaction takes place in a unit called an electrolyzer.
Electrolyzers can range in size from small, appliance-size equipment that is well-suited for small-scale distributed hydrogen production to large-scale, central production facilities that could be tied directly to renewable or other non-greenhouse-gas-emitting forms of electricity production.

Like fuel cells, electrolyzers consist of an anode and a cathode separated by an electrolyte.
Different electrolyzers function in different ways, mainly due to the different type of electrolyte material involved and the ionic species it conducts.

Electrolytes are aqueous or molten.
- In order for electrolysis to occur, compound must be dissolved in water, or melted to form a liquid.
- This means that the ions are free to move around when a current is applied.
Aqueous electrolytes contain water.
- When a compound is dissolved in water, the resulting solution has water present.
- This means that there is both the ionic compound and water molecules in the solution.
Water splits into ions.
- Water molecules can split into two ions: hydrogen ions (H+) and hydroxide ions (OH–). When joined together, they produce water molecules, H2O.

When aqueous electrolytes are involved, electrolysis is slightly more complicated.
Two ions are attracted to the cathode.
- The hydrogen ion and the metal ion are attracted to the cathode. To decide what substance is made at the cathode, we must use the reactivity series.
Metal reactivity is compared to hydrogen.
- If the metal element formed during electh
- Electrolysis is more reactive than hydrogen, then hydrogen will be produced at the cathode.
- If the metal element formed is less reactive than hydrogen, then the metal is produced at the cathode.
Two ions are attracted to the anode.
- The hydroxide ions and halide ions are attracted to the anode.
- If both are present, then a halogen is formed.If no halide ions are present, then the hydroxide ions are discharged, and oxygen is formed.

The electrolysis of aluminium oxide is an expensive process. Suggest two reasons why
- Because a various electricity is required in extraction process. Aluminium is most abundant and is metal in the Earth’ crust
In electrolysis, what is the name of the negative electrode?
- Cathode
What happens at the anode during electrolysis?
- Negative ions lose electrons
What is reduction?
- Gain of electrons