Electrolysis Flashcards
We can only do electrolysis on
Ionic compounds
Sulphate charge
SO4 2-
Nitrate charge
NO3 -
Phosphate charge
PO4 3-
Carbonate charge
CO3 2-
Hydroxide charge
OH -
What happens in electrolysis
Electrical energy is transferred to decompose the electrolyte
What is the Electrolyte
The liquid we are electrolysing
What is the ionic compound broken down into
Positive cations and negative anions
What should the electrolyte be and why
A liquid (molten or dissolved) so that the ions are free to move and carry a current
What current must the electrodes be connected with and why
DC current because the current needs to flow one way so that no electrons are lost
Electrodes and how they work
Negative cathode which attracts positive cations (metals and hydrogen) and a positive anode which attracts negative anions (non-metals and hydroxides) (opposite charges attract)
Electrolysis def
The breaking down (decomposition) of an ionic compound using electric energy from a direct current
Electrode def
A conductor through which electricity enters or leaves a substance
Electrolyte def
An ionic compound (liquid) with free moving ions
Electrolysis of copper sulphate solution
Cu2+ SO4 2- (CuSO4)
The cations copper or hydrogen will travel to the cathode as electrons will leave the cathode. The sulphate or hydroxide anions will travel to the anode. It depends on which ions are less reactive; they will be discharged.
Copper will be made as it is less reactive than hydrogen. The hydrogen ions are donated electrons and become hydrogen molecules.
Oxygen will be made.
Test for sulphur
It’s a yellow gas
Electrolysis of solutions
The less reactive ions will be discharged. A the anode the “simplest” ion is discharged. At the cathode, the metal is discharged if it is less reactive than hydrogen. If it is more reactive, then the hydrogen is discharged.
Inert
Not involved in electrolysis as they don’t react e.g. graphite electrodes (the conduct electricity well)
Anything above carbon uses ____ under uses ____ and silver gold and platinum are extracted from ___
Electrolysis, reduction by being heated with carbon, mining
Ores def
Rocks that contain a metal which we can extract
Malachite
Copper
Bauxite
Aluminium
Cinnabar
Mercury
Galena
Lead
Haematite
Iron
Reduction is the loss of ____ and gain of ____
Oxygen and electrons (to the cathode)
Oxidation is the gain of ____ and loss of ____
Oxygen and electrons (from the anode)
Reducing agent
Causes other things to reduce/steal their oxygen
Spectator ion
Ions that have been left out as they don’t change
Why recycle
Resources are finite and limited, sustainable, energetically favourable, cheaper, avoids landfills which are bad for the environment, less CO2, use less fossil fuels
Life cycle
Obtaining and processing raw materials, manufacturing and packaging product, using product, disposal of product
Formation of copper chloride solution products
CuCl2
Cu2+ + 2e- –> Cu at the cathode (reduction)
2Cl- –> Cl2 + 2e- at the anode (oxidation)
Formation of water acidified with sulphuric acid products
H2O + H2SO4
2H+ + O2- + 2H+ + SO42-
…
REDOX reaction of magnesium and copper sulfate
Copper + magnesium sulfate (displacement)
(Cu + MgSO4)
(Reduction) (Oxidation)
Formation of molten lead bromide products
PbBr2 is a pure substance with only lead and bromide ions. It is the electrolyte. The electrodes are put into the electrolyte and a direct current (battery or cell) applies the electricity. The positive lead ions migrate/transit to the negative cathode and the negative bromide ions migrate/transit to the positive anode.
Cathode: Pb2+ + 2e- –> Pb
Anode: 2Br- –> Br2 + 2e-
