Electrolysis

Electrolysis

is the decomposition of an ionic compound to its elements using electric current

Cathode charge

negative

Anode charge

positive

What happens at electrodes?

ions lose their charge and become elements

What happens at the cathode of lead bromide?

Pb2+ + 2e- → Pb reduction

What happens at the anode of lead bromide

2Br- → Br2 + 2e- oxidation

What are the ions of H2O

H2O → H+ + OH-

What is the rule at the cathode of aqueous solutions

The elements that are less reactive than hydrogen will get discharged

metals less reactive than hydrogen

copper, gold, silver, platinum, mercury

What is the half equation of hydrogen at the cathode

2H+ + 2e- → H2

What is the rule at the anode of aqueous solutions

If there is a halide, it will get discharged over hydroxide

what is the difference between concentrated halide solution and dilute in electrolysis

in a concentrated solution halide is discharged, in a dilute solution hydroxide is discharged

What is the half equation of hydroxide at the anode

4OH- → 2H2O + O2 + 4e-

Aluminium uses

pans, aeroplanes, drink cans, windows, power cables

What is the process of electrolysing aluminium oxide

Bauxite is purified. Aluminium oxide is mixed with cryolite. Aluminium is reduced

What is the purpose of cryolite

lowers melting point, increases electrical conductivity, improves electrolysis efficiency

At the cathode of aluminium oxide

Al3+ + 3e- → Al

At the anode of aluminium oxide

2O2- → O2 + 4e-

oxygen reacts with hot carbon anodes

C + O2 → CO2

What are the products of the electrolysis of brine

Chlorine, Hydrogen, Sodium hydroxide

Use of electroplating

to protect from corroding, to increase hardness, to save money

What happens at the cathode when electroplating with silver

Ag+ + e- → Ag

What happens at the anode when electroplating with silver

Ag → Ag+ + e-

Active electrodes

react

Inert electrodes

do not react

Phytomining

helps extract copper from land

Bioleaching

is a process that uses microorganism to extract metals from ores