Electrochemical cells
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2 ways of constructing an electrochemical cell
-metal dipped in its ions -platinum electrode with 2 aqueous ions
why is platinum commonly used? Why does it need these features
inert electrically conductive
Electrochemical cell set up
2 half cells joined by wire, high resistance voltmeter and salt bridge
What is EMF
voltage between two cells
purpose of voltmeter?
measure EMF
observation during oxidation
electrode being oxidised gets thinner,as more ions are being dissolved insolution
type of reaction that occurs in electrochemical cells
redox
observation during reduction
electrode being reduced gets thicker,as more ions are receiving electrons
what is used as a salt bridge and why?
KNO3 -the tube has unreactive ions that can move between two half cells to carry the flow of electrons -maintains charge balance -doesn’t interfere with the reaction
Define electrochemical series
A list of half cells and their standard electrode potentials in descending numerical order
What are electrode potentials?
measure of how easily the half cell gives up electrons (oxidised)
In the electrochemical series, which form are the equations written in?
reduction (gains electrons) in equilibrium
Which side of the equation has reducing agents?
Right hand side They are more easily oxidised
Which side of the equation has oxidising agents?
Left hand side They are more easily reduced
Which half cell undergoes oxidation?
More negative half cell
Which half cell undergoes reduction?
More positive half cell
What is SHE?
Standard Hydrogen Electrode Used as a reference to measure standard electrode potentials, because they can’t be measured on their own
Standard conditions for electrochemical cells?
298K 1.00 mol dm-3 100kPa
Which is the strongest reducing agent?
Most negative half cell
Which is the strongest oxidising agent?
Most positive half cell
Formula to calculate standard cell potential
E r - E o
How to draw cell notation?
Reduced | Oxidised || Oxidised | Reduced Most negative half cell goes on the left
Anticlockwise
Oxidised is on top of reduced Combine both equations to obtain a feasible reaction Use the formula Positive value = feasible
What are the two forms of batteries?
Rechargeable and non-rechargeable