Electrochemistry
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Electrochemistry
Redox reactions can be studied electrically using…?
electrochemical cells
What is an electrochemical cell?
an electrochemical cell is a simple system that generates a voltage
Draw a diagram to show an electrochemical cell made up of 2 half-cells connected by a salt bridge
What are the metal strips?
these are called electrodes (metallic conductors)
What does each beaker contain?
each beaker contains a half-cell made up of redox couple
What does a redox couple consist of?
a redox couple consist of metal atoms in equilibrium with it’s aqueous solution of ions
In this experiment, which two things need to be connected in order for a reaction to occur?
No reaction can occur until the 2 half cells are connected by an external circuit (and a salt bridge)
What is the external circuit?
The external circuit is a conducting wire through which electrons can pass from one electrode to the other.
What is the salt bridge?
The salt bridge is a strip of filter paper soaked in a solution of soluble ionic compound (e.g potassum nitrate or potassium chloride)
What is the salt bridge usually soaked in?
Potassium Nitrate or Potassium Chloride
Electrode Potentials
What is the external Circuit?
The external circuit is a conducting wire through which electrons can pass from one electrode to the other
What is the salt bridge?
the salt bridge is often a strip of filter paper soaked in a solution of a soluble ionic compound(e.g potassium nitrate or potassium chloride) that does not react with the contents of either beaker
What is the role of the salt bridge?
• the salt bridge enables the cell to work by completing the circuit without the 2 solutions mixing • the salt bridge allows ions to move between the 2 half-cell compartments • it prevents ion saturation at the electrodes that would stop the cell from working
when does a voltmeter measure a reading?
when there is a potential difference between the 2 half-cells
What is a voltmeter reading called?
A cell potential
Draw and label a cell diagram
The cell diagram can be written in a shorthand notation. Write the shorthand notation for RH magnesium electrode and a LH copper electrode. Describe what each thing notation represents?
• Positive electrode = written/drawn on the right hand side • single vertical lines = represent phase (state) boundaries • double vertical lines = salt bridge • metal electrodes = always on the outside • oxidation occurs in the Left hand half-cell and reduction occurs in the Right hand half-cell
Describe the flow of electrons according to the cell diagram and the shorthand cell diagram?
electrons flow from the left hand half-cell to the right hand half-cell via the external circuit
What type of reaction occurs in the Left-hand half cell and what type of reaction occurs in the right hand half-cell?
Left = Oxidation Right = reduction
Factors that affect the cell potential
What are the factors that affect the cell potential?
• cell current • cell concentration • cell temperature • cell pressure
What is the cell current/ what is it measure by?
a high resistance digital voltmeter must be used to measure the true cell potential