Electrode Potentials Flashcards
What is MnO4- oxidised to
Mn2+
What is Cr2O7 2- oxidised to
2Cr 3+
What is electrode potential
The potential difference between 2 half cells that make up a cell
How is an electrochemical cell produced
When 2 half equations are joined together
What side is the negative electrode always on
The left
Which equation is flipped and why
The negative one
Because they are always written as reduction equations
The negative one is oxidised
What is the equation for calculating emf
Epos- Eneg
What does a salt bridge do
Allows the transfer of ions between the cells in order to balance the charge
What salt can the salt bridge be filled with an what is a condition of it
Must be inert
Saturated Potassium nitrate or sodium chloride solution
Why is a high resistance voltmeter used to measure voltage
Prevents electrons from marvelling continuously form one half cell to another which keeps current low therefore safer
What is the reference electrode
The standard hydrogen electrode
What side is the standard hydrogen electrode always on
Left side
Draw a standard hydrogen electrode
Photo
What is the condition for measuring standard hydrogen potentials (2)
All ages at 100kpa
All solutions with conc 1.00 mol dm-3
Why platinum used as an electrode in cells with no metal (3)
Good electrical conductor
Inert
Doesn’t react with electrolyte
Which ones are the best reducing agents
Most negative
Which are the best oxidising agenrs
Most positive
To oxidise does the e value have gone higher or lower
Lower / more negative
To reduce does the e value have to be higher or lower
Higher / more positive
In half equations which ones are you here oxidising and reducing agents
The ones in the right are reducing agents
The ones on the left are oxidising agents
What happens to e cell value of concentration of reactants are increased
Equilibrium will shift to the right and e value of half cell increases
What happens to e cell value if concentration of products is increased
Equilibrium shifts to the left and e cell value for the half cell decreases
What are the2 types of cell
Chargeable - primary cells - only used once
Rechargeable - secondary cells - can be recharged and reused
What is the lithium ion cell used in
Mobile phones and laptops
What is the anode and cathode of a lithium ion cell
Lithium cobalt oxide
Carbon graphite
Refer to photo
What are the half equations in a lithium ion cell
Photo
How are cells rechargeable
By reversing the cell reactions by applying an external voltage to drive electrons in the opposite directions
What type of system is a fuel cell
An open system - the reactants flow in and out rather than being stored
What do commercial hydrogen oxygen cells used and why
Porous platinum electrodes in contact with concentrated KOH to increase surface area
Why can hydrogen fuel cells be polluting
Processed used or produce the hydrogen for example electricity for electrolysis by fossil fuel power stations
And carbon dioxide from reaction if hydrocarbons with steam
