Slides in this set
What are electrochemical cells?
· Made from two different metals dipped in salt solutions of their own ions and
connected by a wire.
· The wire is the external circuit.
· Half-cells involving solutions of two aqueous ions of the same element use a
Conversion of ions happens on the surface of the electrode.
· Half-cells are connected by a salt bridge made of filter paper soaked in KNO3
K+ and NO3- ions flow through the salt bridge and balance out the charges in the two
· Redox reaction occurs in an electrochemical cell.
Electrons flow through the wire from the most reactive metal to the least reactive
· Voltmeter in the external circuit shows the voltage between the two half-cells.
This is called the cell potential or emf, Ecell.
Ecell = ERHS - ELHS
More negative standard electrode potential put on the left, so the cell potential is
Swapping the sides the half-cells are on changes the sign of the cell potential.…read more
What are electrode potentials?
· Standard electrode potential, E, of a half-cell is the voltage measured under
standard conditions when the half-cell is connected to a standard hydrogen
Standard conditions are solutions at 1M concentration, temperature of 298K and
pressure of 101kPa.
Ecell = ERHS - ELHS
Electrode potential can be positive or negative, depending on which way the
· Standard hydrogen electrode is hydrogen gas bubbled through a 1M solution
of H+ ions with a platinized platinum electrode submerged in, at 101kPa
Platinized platinum electrode means the surface of foil is finely powdered with
The platinized surface absorbs hydrogen gas, causing an equilibrium to be set up.
H2(g) H+(aq) + 2e-
Electrode potential of a standard hydrogen electrode is 0.
Reference cell because it is used to measure the electrode potentials of other half-
Standard hydrogen electrode always put on the left.…read more
What is the electrochemical series?
· The more reactive the metal, the more likely it is to lose
electrons to form a positive ion.
More reactive metals have more negative standard electrode
· The more reactive a non-metal, the more likely it is to gain
electrons to form a negative ion.
More reactive non-metals have more positive standard electrode
· Electrochemical series shows standard electrode potentials.
More positive electrode potentials mean the left-hand substance is
more easily reduced and the right-hand substance is more stable.
More negative electrode potentials mean the right-hand substance
is more easily oxidised and the left-hand substance is more stable.…read more
What is the anticlockwise rule?
· Predicts whether a reaction is likely to happen.
1. Write half-equations out with the most negative standard
electrode potential on top.
2. Draw on anticlockwise arrows to show the direction of the
3. Swap the top half-equation, and change the sign of the
4. Combine the half-equations and find the cell potential.
· Electrode potential chart is another way of showing the
anticlockwise rule; upside down y-axis showing electrode
potentials with the more negative electrode potential on