Production of Materials > 4. Electrochemical Methods >
Perform a first-hand investigation and gather first-hand information to measure the difference in potential of different combinations of metals in an electrolyte solution
- The difference in potential of different combinations of metals in electrolyte solutions can be measured using the following procedure:
- Select two metals (Metal A and Metal B) and arrange them and their solutions as shown below:
Experimental setup
- Observe and record the reading given by the voltmeter.
- If the voltmeter gives a reading of zero, reverse the terminals, and observe and record the reading again.
- If the voltmeter gave a positive reading with the initial terminal arrangement, then Metal B is the more easily oxidised metal, while Metal A is the more easily reduced metal.
- If the voltmeter gave a positive reading after the terminals were reversed, then the nature of the metals is the opposite to the above.
- The voltage reading corresponds to the difference in potential of the two metals.
- Repeat the above procedure with different metals in place of Metal B.
- Use Metal A as a standard (allocate it a potential of zero) to create a table of approximate reduction potentials using the results obtained.
- In reality, the standard hydrogen electrode is the chosen reference electrode, and is allocated a potential of zero.
- The standard hydrogen electrode consists of:
- Platinum foil coated in fine platinum powder dipping into a solution containing 1 mol. L-1 hydrogen ions.
- Hydrogen gas of 100 kPa pressure and 25°C temperature bubbling over the electrode.
- When the standard hydrogen half-cell forms one half of a galvanic cell with another half-cell, then the potential difference of the whole cell is a measure of the standard electrode potential of the second half-cell.
Example setup using copper and zinc