Electrochemistry (CDS)
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Ions with a higher electrode potential will ___ electrons and be _____
attract, reduced
Ions with a lower electrode potential will ____ electrons and be ____
repel, oxidised
Why do we use a salt bridge instead of a wire in an electrochemical cell?
Because wires can only transfer electrons whereas the salt bridge can transfer ions.
Standard conditions for measuring electrode potentials
1 mol dm-3 298K or 25 degrees celsius 100kPa Current = 0
Why do we use strong acids like HCl in the SHE?
They fully dissociate into their ions in water, providing a solution of H+ ions
Why do we use a platinum wire and electrode in the SHE? (2)
• Can’t attach an electrode to a gas • Platinum used as it’s highly unreactive and won’t corrode or react with electrolyte
How does the SHE allow us to find the electrode potential of a half cell?
The potential of the SHE is defined as zero, so when connected to another electrode, the measured voltage, or electromotive force (emf) of the cell, is the electrode potential of that cell.
Electrodes with negative electrode potentials are better ______ agents.
reducing
Electrodes with positive electrode potentials are better ______ agents.
oxidising
In an electrochemical cell H is always _____
oxidised
How to calculate the potential difference of an electrochemical cell?
E°cell = E°cathode - E°anode E°cell = E°right - E°left
EMF of a hydrogen oxygen fuel cell
1.23 V
Advantages of fuel cells over internal combustion engines
• Higher efficiency - Convert a greater portion of their available energy into kinetic energy, while internal combustion engines lose a significant amount of energy as heat. • Clean emissions - No carbon emissions jus water • No recharging required - As long as hydrogen and oxygen are supplied, fuel cells will continue to generate electricity without the need for recharging.
Disadvantages of fuel cells
• Demands significant energy input to make H and O. This electricity is often generated by burning fossil fuels, so the overall process may not be carbon-neutral. • Flammability concerns - Hydrogen gas is highly flammable, necessitating careful handling during storage and transportation to ensure safety.