Electrodes Flashcards
(29 cards)
Drawing a electrochemical cell
2 beakers with solution in standard states of 1moldm-3 and its electrode if it doesn’t have an electrode than use platinum as its inert which means it’s unreactive and conduct electricity, has poring coating to provide a large surface area
Salt bridge which is made of KNO3 =. Allows movement of electrons
2 wires connected to a voltmeter which measures how hard the electrons are being pushed ( EMF) =eg power supply to car
Why is platinum a good electrode
Inert
Conduct electricity
Has a porous coating which gives it a large surface area
What is salt bridge made off and why is it a good thing
KNO3
Allows moving of electrons
Combining equations
look at emf number, the lowest number equation = swap and combine by making sure number if electrons are equal.
Recharging = opposite to what it is
Key thing to always remember
POSITIVE RIGHT REDUCED
Draw a Standard hydrogen electrode
Standard conditions =1moldm-3 of H+ IONS 298k,100kpa,
The left hand side = H2 gas pumped in at 100kpa , 298k into platinum electrode with a 1moldm-3 solution of HCl/ 0.5 mol of H2SO4
Right electrode = 1moldm-3 of solution
What is a SHE used for
Has a voltage of 0v by definition so can measure electrode potential
Electrochemical series
List of half cell reactions and their standard electrode potential.
How to find strongest oxidising agent
Use SOWR AND WOSR to find strongest/ weakest reducing agent. Make sure you look at which order the numbers are . More positive = stronger oxidising agent
Calculating standard cell potential
Calculating standard cell potential = reduced - oxidised
Cell notation
ROOR = electrode on far right or left ( oxidised = more positive number)
Double line = salt bridge and single line = change in state think reactant product
Standard conditions
1moldm-3 of H+ IONS 298k,100kpa,
Concentration of mg2+ decreases
Conditions are importantly otherwise equilibrium could occur. Left more right. Fewer, greater electrons, more positive or negative standard electrode potential
Rechargeable batteries
Made of lithium ions which are used in smartphones and is a low density metal
Negative electrode= li=li+ + e-
Positive electrode= lithium ion combined with CoO2
CoO2 + ki+ +e- = Li(CoO2)
At the negative electrode of batteries
li=li+ + e-
At the positive electrode
CoO2 + ki+ +e- = Li(CoO2)
Conventional cell representation
li,li+,,li1+,CoO2,li(COO2),pt
Fuel cell advantages instead of using fossil fuels
Greater efficiency than burning hydrogen in combustion engine
Less polluting as water is the only product
Disadvantage of using fuel cell compared to fossil fuel
Hydrogen is difficult to store
Fossil fuels are combusted to produce the hydrogen which releases carbon dioxide
Advantages of fuel cells compared to other types of cells
Voltage is constant as constant supply of oxygen and fuel
Acid fuel cell
At the negative electrode= hydrogen is oxidised into H+ ions and electrons
H2 = 2H+ +2e
Some electrons transferred to a wire connected to the positive electrode and where a car would get its electricity from
Hydrogen ions are transferred through the membrane
At the positive electrode O2 + H+ + 2e- = H2O
Water is formed only
Conventional representation
Pt,H2,H+,,O2,H+,H2O,pt
Alkaline fuel cell
In an alkaline solution at the negative electrode, H2 +OH- =H2O + 2e-
At the positive electrode = O2 + H2O + 2e-= OH-
Recharging
Opposite to what it is
