Electrochemical cells Flashcards
Electrochemical cell
A device used to produce electric current from a chemical reaction. It is constructed from two half cells
What side i the more negative half cell
Left
The 4 rules
1) Solid vehicle line represents a phase boundary (where two different states meet)
2)Salt bridge is represented by double dotted line
3)Two most reduced species shown on the outside
4) more negative half cell is on the left
The exception to rule 4
If. A half cell is connected to a standard hydrogen electrode, then the hydrogen electrode is both drawn an written on the let
Define standard electrode potential
The electromagnetic force of a cell containing the half cell connected to the standard hydrogen electrode
Standard conditions apply: 298K, 100KPa, 1 Moldm-3 ion concentration
Why a reference electrode is needed to measure a metal ion electric open tail
Electrode is used to complete he circuit
Standard hydrogen electrode used because it does not interfere with the reading unlike other metals
What a negative value of standard electrode potential means (E cell)
Species readily loses electrons
Equilibrium lies to the left
Salt bridge
Filter paper soaked in KNO3
Use this because all K and NO3 slats are soluble so no precipitate will be formed that would interfere with the reading
Negative E0 value for half cell
Electors flow from the half cell to the hydrogen electrode
Positive E0 value for half cell
Electrons flow from hydrogen electrode to half cell
EMF
Electromotive force
Potential difference when no electrons are flowing through the circuit
Ecell
ΔGθ
ΔGθ = -nFEθcell
Relationship between ΔStoal and Ecell
Directly proportional
If E cell is negative, is the reaction feasible
No
