Unit 3 - Topic 2 - Electricity and Chemistry Flashcards
Describe electrolysis
Electrolysis takes place when electricity is passed through an ionic compound in solution or in the liquid state.
A solution that conducts electricity is called an electrolyte.
Describe the electrolysis of Copper (II) Chloride
The copper ion in copper (II) chloride has a positive charge, therefore,
it is attracted to the negative electrode
The chloride ion has a negative charge, therefore, it is attracted to the
positive electrode.
Why is a d.c current used?
To clearly identify the products.
Describe what happens at the positive electrode
The chloride ion is attracted to the positive electrode because the chloride ion is negatively charged.
At the positive electrode, the chlorine will lose an electron to become chlorine gas.
This loss of electrons is called oxidation.
Describe what happens at the negative electrode
The copper ion is attracted to the negative electrode because the copper ion is positively charged.
At the negative electrode, the copper (II) ion will gain 2 electrons to become copper metal.
This loss of electrons is called reduction.
Describe reduction
Reduction is the gain of electrons
Whenever a metal is extracted from its ore, the metal is reduced.
In a reduction ion electron equation, the electrons (e-) are always on
the left of the arrow.
Describe oxidation
Oxidation is the loss of electrons.
In a oxidation ion electron equation, the electrons (e-) are always on the right of the arrow.
Describe redox
Oxidation and reduction occur at the same time. If one substance is
oxidised, the other is reduced. This is called a redox reaction.
Describe simple cells
A simple cell (or battery) can made by joining zinc to copper
An electrical current flows from the zinc electrode to the copper electrode
For zinc atoms to produce electrons they have to change into zinc ions
The zinc atoms are oxidised as each atom loses 2 electrons
The salt solution is an electrolyte. The ions in the salt solution completed the circuit
Describe electrolyte
Compounds which conduct electricity when molten or in aqueous solution are
called ELECTROLYTES.
Regularly, electrolytes are used to complete circuits.
All ionic compounds are electrolytes.
All cells (batteries) require electrolytes.
Describe simple batteries
A simple battery is called a cell
All metals change into their ions, giving off electrons when they react.
However, different metals are not equally good at changing into their ions.
The electrons, which come off the metal atoms, build up on the surface of the metal.
Measuring the voltage between two different metals gives a measure of the difference in
their abilities to change into their ions and give off electrons.
Summarise electrochemical cells
In a simple cell, the metal that is higher up in the electrochemical series is oxidised (lose electrons). The mass of the oxidised metal will decrease.
The metal that is lower down in the electrochemical series will be reduced (gain
electrons).
The further apart the metals in the in the electrochemical series, the larger the voltage.
Electrons flow through the wire from the metal higher to the metal lower in the
electrochemical series.
The ionic solution is an electrolyte. It completes the circuit.
Describe electrochemical cells in more complicated cells
The metal higher in the reactivity series is oxidised, the metal lower in the reactivity series is reduced.
The metal electrode that is oxidised will decrease in mass.
The electrons flow through the wire from the metal that is oxidised to the metal that is reduced.
What does electrochemical cell mean
An ELECTROCHEMICAL CELL makes an electric current from chemicals.
This name is often shortened to a CELL.
Describe the salt bridge
The electrochemical cell does not work without a salt bridge. Another name for a
salt bridge is an ion bridge
The ion bridge ensures the solutions are always electrically neutral by allowing ions to move between the solutions.
