Electrodes Flashcards
Half cell
It is one half of a electrochemical cell. Can be constructed of a metal dipped into into metal ions or a platinum electrode with 2 aqueous ions
Electrochemical cells
These are made to two half cells joined together by a voltmeter and salt bridge
What is voltmeter
Voltmeter is used to measure the potential difference between two half cells
Also prevents electrons flowing
Salt bridge
Made of KNO3
Allow movement of ions which balances the charge
Why salt bridge is made of KNO3
Because KNO3 is unreactive and ions are free to move
Direction of flow of electrons in electrochemical cell
Electrons move from more reactive to less reactive metal
From left to right always
Why might current produced by cell fall to zero after sometime
All reactants are used up
What happens once cell reactants are used up
Stop working or start to leak
Why is Standard hydrogen electrode used?
To compare the potential of electrode of a half cell
General set up for SHE
H2 gas is pumped in at pressure of 100KPa
Temperature of whole system 298K
Concentration of ions is 1 mol/dm3
Platinum should be used as electrode
Which specie should be the closest to salt bridge
specie with highest oxidation state
Cell representation of standard hydrogen half cell
Pt/H2/H+//
The standard hydrogen electrode is always on the left side
Give an environmental advantage of using rechargeable cells
metal is reused
what is the disadvantage of using rechargeable cell
uses electricity to recharge which can be produced by the burning of fossil fuels which release CO2
what is an electrolyte
an electrolyte is a part of battery that acts as conductive pathway for the ions and allow ions to move from one electrode to another
conventional cell representation of lithium ion battery
Li/Li+//Li+,CoO2/Li(CoO2)/Pt
recharge battery equation
reverse positive right reduced
reverse discharging equation of positive right reduced
why some batteries are single use battery
because the electrochemical reaction taking place in them is irreverseable
Advantage of using fuel cells for energy instead of fossil fuels
Greater efficiency than burning hydrogen in combustion engine
less polluting as water is the only product
Disadvantage of using fuel cell over fossil fuel cells
H2 is difficult to store
Fossil fuels are combusted to produce hydrogen which releases CO2
Advantage of fossil fuels compared to other types of cells
Voltage is constant as fuel and oxygen supplied constantly so concentration of reactants remain constant
Suggest the effect if any on the cell if the surface area of each platinum electrode is increased.
Unchanged
Environmental advantage of using hydrogen fuel cell
Less pollution as water is the only product
Why use of a hydrogen oxygen fuel cell might not be carbon neutral
CO2 produced as fossil fuels are used to generate electricity to generate hydrogen
