1.11 Electrode Potentials Flashcards
1
Q
why does a voltage form across two half cells?
A
- one half cell has a greater tendency to oxidise an ion and release electrons than the other
- more electrons will build up on one electrode
- creating a potential difference between the electrodes
2
Q
why do we use a high resistance voltmeter?
A
- to stop current from flowing in the circuit
3
Q
what is the salt bridge?
A
- connects the circuit
- should be unreactive with electrodes and electrode solution
- made from a piece of paper soaked in a salt solution
4
Q
what happens to the most positive electrode
A
- reduction, ions accept electrons
5
Q
what happens to the more negative electrode
A
- oxidiation, electrons are given off
6
Q
how does cell notation work?
A
- write both reduction equations for the elements
- determine which undergoes oxidation/reduction
- starting from left of cell, write the oxidation equation, then the reduction
- seperate with a salt bridge
7
Q
what happens if a system doesnt inclue a metal?
A
- use a platinum electrode
8
Q
why do we use a platinum electrode?
A
- inert
- provides conducting surface for electron transfer
- electrically conductive
9
Q
what is the standard hydrogen electrode used for?
A
- measures potential of all electrodes by comparing them to SHE
- SHE is assigned e potential of 0V
10
Q
what are the standard conditions required?
A
298K
100kPa
both ion solutions have to have a concentration of 1moldm^-3
11
Q
what will happen to the electrode potential if hydrogen ion concentration is reduced
2H+ + 2e > H2
A
- reducing H+ concentration causes equilibrium to shift to the left to reduce this change
- this will cause electrode potential to become more negative
12
Q
what is the equation for electrode potential?
A
E reduced - Eoxidised = Ecell
