Electrode potentials Flashcards
What happens when a metal is placed in a solution of its ions?
An equilibrium is established between the ions in solution and the metal atoms
Represent the equilibrium by a half equation
M^n+(aq) + ne- ⇌ M(s)
What are the half equations always written as
Reductions, Electrons on LHS
What are two half cells combined called?
A cell
What is the standard electrode potential?
The potential difference measured when a half cell is connected to the standard hydrogen electrode under standard conditions 1moldm-3 and 298K
What are electrode potentials represented by and what are they measured in?
Represented by E⦵ and measured in Volts
What is the electrode potential?
A measure of the feasibility of the reduction occurring
What does a negative E⦵ suggest?
That the reduction will not occur unless a more feasible oxidation takes place
What is emf?
The potential difference measured when two half cells are connected
What does a positive emf indicate?
A feasible reaction
What does a negative emf indicate?
Unfeasible reaction
What does the emf always relate to?
The overall redox equation, oxidation and reduction combined
What are the five features of the standard hydrogen electrode?
- Platinum electrode
- 1.00 moldm-3 hydrogen ions in solution
- H2 gas at 100kPa
- Temperature 298K
- Standard electrode potential = 0.00V
How do you combine two half cells?
Combined using a salt bridge and an external circuit using a high resistance voltmeter to produce a cell
How do you make the salt bridge?
Filter paper soaked in potassium nitrate solution which dips into both solutions
What is the purpose of the salt bridge?
Allows electrical connection between the two half cells without them having to mix
What usually are the left and right hand cells?
Left hand cell is the one in which oxidation occurs and is the negative electrode of the cell
Right hand cell is the one in which the reduction occurs. It is the positive electrode of the cell
How do you remember where oxidation occurs
NEGATOX
Negative electrode is the one at which oxidation occurs