Electrode potential 6 Flashcards
Define standard electrode potential
The voltage measured under standard conditions. When the half cell is connected to a standard hydrogen half cell
What are the standard conditions
. 298K
. 101KPa
. 1 moldm-3
Why is platinum( or graphite) used as an electrode
It is inert
Why are the electrodes connected by a wire
To allow the electrons to flow
Why are the solutions connected by a salt bridge
To complete the circuit and to allow the ions to flow into the half cell to maintain the neutrality of the half cells
What is the salt bridge typically made up of
Filter paper soaked in KNO3(aq)
Describe the procedure how to set up cells to measure standard cell potential
- Prepare two standard half cells
- Connect the two electrodes of the half cells to a voltmeter using wires
- Prepare a salt bridge by soaking a strip of filter paper in a saturated solution of KNO3
- Connect the two solutions of the half cells with a salt bridge
- Immediately record the standard cell potential from the voltmeter
How to calculate the cell potential
E(red)-E(ox)
Describe the limitations of the prediction of cell potential when its in non-standard conditions
If any conditions alter, the cell potential values are also altered. It will affect the reaction
Describe the limitation of the prediction of cell potential of reaction rates
. The reaction does not happen as the activation energy is too high causing the rate of reaction to be too slow
Describe the limitation of the prediction of cell potential when changing concentration
Changes the equilibrium of the reaction
Define Le Chatelier principle
When the conditions affecting the position of a dynamic equilibrium are changed, then the position of the equilibrium will change to minimise the change
Define Primary/ Non-rechargeable cells
They provide electrical energy until the chemicals have reacted and the voltage falls, and its discarded
Define Secondary/ Rechargeable cells
Chemicals in the cell react to provide chemical energy, the cell reaction can then be reversed during recharging ( the chemicals are regenerated)
Define fuel cells
Uses the energy from the reaction of a fuel cell with oxygen to create a voltage. Both fuel and oxidant are used up during reaction and need to be continuously provided if the cell is to continue to provide energy.
