DM - Electrochemical cells Flashcards
What do you get when electrons move?
Electricity
What do electrochemical cells make?
Electricity
What can electrochemical cells be made from?
Two different metals dipped in salt solutions of their own ions and connected by a wire (the external circuit).
What do two different metals dipped in salt solutions of their own ions and connected by a wire (the external circuit) make up?
Electrochemical cells
There are always how many reactions within an electrochemical cell?
2
What two reactions are there always within an electrochemical cell?
Oxidation
Reduction
What type of process is going on in an electrochemical cell?
A redox process.
Where in an electrochemical cell does oxidation always happen?
At the anode (the positive electrode).
Where in an electrochemical cell does reduction always happen?
At the cathode (the negative electrode).
Which electrode is positive?
Anode.
Which electrode is negative?
Cathode.
Is the anode positive or negative?
Positive.
Is the cathode positive or negative?
Negative.
What happens in a zinc/copper electrochemical cell?
1) Zinc loses electrons more easily than copper. So in the zinc electrode half-cell, zinc (from the zinc electrode) is OXIDISED to form Zn^2+ (aq) ions.
Zn (s) –> Zn^2+ (aq) + 2e-
This releases electrons into the external circuit.
2) In the other half-cell, the same number of electrons are taken from the external circuit, REDUCING the Cu^2+ ions to copper atoms.
Cu^2+ (aq) + 2e- –> Cu (s)
Where do electrons flow in an electrochemical cell?
Through the wire from the most reactive metal to the least.
How are the solutions in the two half-cells connected?
By a salt bridge made from filter paper soaked in a salt solution, e.g. KNO3 (aq).
What is the salt bridge for?
The salt ions flow through the salt bridge to complete the cell, and balance out the charges in the beakers.
What is included in the external circuit?
A voltmeter.
What does the voltmeter do in the external circuit?
Shows the voltage between the two half-cells.
Also measures the direction of the flow of electrons.
What is the cell potential or EMF, Ecell?
The voltage between the two half-cells.
What is the voltage between the two half-cells called?
The cell potential or EMF, Ecell.
What can half-cells involve?
Solutions of two aqueous ions of the same element, such as Fe^2+ (aq)/Fe^3+ (aq).
Where does the conversion from Fe^2+ to Fe^3+ (or vice versa) happen in an electrochemical cell?
On the surface of the electrode.
Equations showing conversion of Fe^2+ to Fe^3+ (and vice versa)
Fe^2+ (aq) –> Fe^3+ (aq) + e-
Fe^3+ (aq) + e—> Fe^2+ (aq)