REDOX AND ELECTRODE POTENTIALS Flashcards
5 steps to forming half equations
- write down the species before and after a reaction
- balance any atoms apart from oxygen and hydrogen
- balance any oxygen with H2O
- balance any hydrogens with H+
- balance charges with electrons
2 ways a half cell can be constrcuted
a metal dipped in its own ions
platinum electrode with 2 similar solutions ions
why is platinum used in a half cell with 2 aqueous ions
as it is very unreactive but is electrically conductive
how are electrochemical cells constructed
2 half cells joined by a wire, voltmeter and a salt bridge
which way do electrons flow in an electrochemical cell and describe the observations seen
from a more reactive metal to a less reactive metal
less reactive metal is reduced and more reactive metal is oxidised
less reactive electrode will thicken and the more reactive electrode will get thinner
Why is a salt bridge used and what solution does it contain
used so that ions can flow through in order to balance the charges
KNO3 saturated filter paper
What does electrode potential of a half cell show
how easily the half cell gives up electrons
What is the NO PRoblem rule
the most Negative half cell is being Oxidised
the most Positive half cell is being reduced
What side of the equation are the electrons in a reduction and an oxidation of a half cell
electrons are on the left if the half cell undergoes reduction
electrons are on the right if the half cell undergoes oxidation
How is the standard hydrogen electrode setup and what does it show
H2 goes in at 298 kelvin at 100kPa into a glass tube around a platinum electrode in a solution of 1 moldm-3 H+ ions
the standard hydrogen electrode potential is 0 so voltmeter will show the standard electrode potential of the other half cell assuming all conditions are met
How to calculate the standard cell potential
Ecell = Ereduced - E*oxidised
red-ox
How are cell notations drawn
Most negative half cell on the left
Most positive on the right
Reduced Form | Oxidised form | | Oxidised form | Reduced form
Solid single lines show physical state changes
Solid double line shows the salt bridge
IF IONS ARE AQUEOUS USE A COMMA RATHER THAN A SOLID LINE
What is the cell potential value if the reaction is feasible
positive E*cell values show the reaction is feasible
What factors can affect electrode potential
temperature, concentration can alter the half cells ability to lose electrons
