3.1 Redox and Electrodes Flashcards
oxidation in terms of electron transfer??
loss of electrons
reduction in terms of electron transfer??
gain of electrons
redox rctn??
a redox rctn of a rctn in which oxidation & reduction occur on diff species simultaneously
standard electrode potential??
standard electrode potential is the potential across the electrodes when a redox system is connected to a hydrogen half-cell under standard conditions
conditions req for measuring the standard electrode potential??
298K temp
100kPa pressure
1.00 moldm^-3 conc of ions
why is a hydrogen half-cell needed as a reference??
the hydrogen half cell is used to allow for easy comparison between the electrode potential of diff elements. the standard electrode potential for hydrogen is assumed to be zero volts at any temp
experimental setup to calc the standard electrode potential for zinc??
the hydrogen standard cell is always placed on the left
diagram of 2 beakers left w H2 intotube connecting to Pt cathode in HNO3 soln w H+ in it salt bridge connecting 2 solns voltmeter connectinf cathode to Zn anode right soln Zn(NO3)2 w/ Zn2+ in sol
why must metal electrodes be cleaned w sandpaper before creating electrochemical cell??
to remove any metal oxide on surface improving electrical conductivity
describe movement of electrons in electrochemical cell??
electrons flow thru wire from +ve electrode to -ve electrode
why is s salt bridge used in an electrochemical cell??
to maintain the charge balance & complete the ircuit, -ve electrons are moving from 1 half cell to another, w/o salt bridge +ve charge would build up in half cell containing the anode & -ve charge would build up in halfcell containing cathode causing rctn to stop
what moves across the salt bridge??
ions
why must an inert salt be used in the salt bridge??
the salt must be inert so that it doesn’t react w/ the solns & alter the ion concs, if a reactive salt was used the cell potential would change
for what range of cell potential values is a process feasible??
cell potential must be greater than 0
how can cell potential be calculated??
Ethetacell =
Etheta +ve - Etheta -ve
why might theoretical cell potential values be diff to values obtained experimentally??
conditions may be non-standard
