Electrode Potentials And Cells Flashcards
How can electrochemical cells be made
From 2 different metals dipped in salt solutions of their own ions and connected by a wire (the external circuit)
what are the 2 reactions that occur
An oxidation and a reduction
In a copper and zinc cell.. Which cell is oxidised and which is reduced
Zinc loses electrons more easily than copper, so in the half cell on the left, zinc is oxidised to form Zn2+.
Therefore copper is reduced from Cu2+ to copper atoms
What is EMF
The voltage between the 2 half cells
Cell potential
What does the direction of the reaction depend on
How easily each metal loses electrons (easily its oxidised)
Measured using electrode potentials
A metal that’s easily oxidised has a very negative or positive electrode potential
Very negative
In what order to we draw half cells
ROOR
Which half cell do you always put on the left
The one which has the more negative electrode potential
Equation for EMF
E cell = E right - E left
What factors effect the electrode potential
Temperature
Pressure
Concentration
SHE
Pt | H2(g) | H+(aq) ||
EMF 2nd equation
E cell = E reduced - E oxidised
Steps to predict the direction of reactions
1) find the 2 half equations for the redox reaction
2) use electrochemical series to work out which half-equation has the more negative electrode potential
3) write out the half equation with the more negative electrode potential going in the backward direction (oxidation) and the half equation with the more positive potential going in the forward direction
4) combine the 2 half-equations and write out a full redox equation
How do you know which the feasible direction of the reaction is
A positive overall E cell value
What kind of reactions do non-rechargeable cells use
Irreversible reactions
