electrode potentials allery Flashcards
what is a half cell
- one of an electrochemical cell
how can a half cell be constructed
- metal dipped in its ions, or platinum electrode with 2 aqueous ions
why do we use platinum with the 2 aqueous ions?
- platinum is inert
- electrically conductive electrode
what is an electrochemical cell
- created by joining 2 different half cells together
what is an electrochemical cell made up of?
- wire
- voltmeter
- salt bridge
what happens when we connect 2 half cells
- one side undergoes a reduction process
- other side undergoes an oxidation process
- redox reaction occurs essentially
what is the voltmeter used for
- to measure the potential difference between the 2 half cells
how do the electrons flow?
- from a more reactive metal to a less reactive one
what happens when a half cell oxidises?
the electrode becomes thinner as more of the ion is produced to make the electrons
what happens when a half cell reduces
the electrode will get thicker as ions receive the electrons and turn into copper
whats the role of the salt bridge
- completes the circuit
- filter paper with saturated KNO3 solution
- ions flow through which balances the charges
what is electrode potential
- how easily the half cell gives up electrons
how do we write equations in electrochemical cells
- in the reduced form
- we always show the equations with reduction in the forward direction
- electrons on left side
how can we determine which half cell is being reduced and oxidised
- look at electrode potential value
- found in data book
what happens if a half cell has a negative electrode potential value
it undergoes oxidation
what happens if a half cell has a positive electrode potential value
- it undergoes reduction
acryonym NO PRoblem
- negative oxidation
- positive reduction
what is the STANDARD HYDROGEN ELECTRODE
- used as a reference to measure standard electrode potential
how do we setup the SHE
- temp at 298K
- pressure at 100kPa
- concentrations of ions at 1moldm-3
what is the electrochemical series
- list of half cell reactions and their standard electrode potentials
what does a positive value in the electrochemical series tell us
- is is a more powerful oxidising agent
how do we calculate the standard cell potential
E. = E. reduced - E. oxidised
redox
how and why do we use cell notation?
- standard way of representing cells in chemistry
Reduced form | oxidises form || oxidised form | Reduced form
what does a double line in a cell notation show
salt bridge
how do we setup cell notation
- most negative half cell potential goes to the left of the double line