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34 Cards in this Set
- Front
- Back
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How is an equilibrium set up in half cells? |
Rod of metal is dipped into a solution of its own ions |
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What does the position of equilibrium determine in half cells? |
The potential differences (and the value of the electrode potential between the metal strip and the solution of metal |
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How is an electrochemical cell created? |
2 half cells joined together |
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What is the function of the salt bridge? |
Allows the transfer of ions to balance the charge in each half cell |
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What is the salt bridge made of? |
Usually a hollow glass tube filled with a salt such as potassium nitrate |
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Why must the salt in the salt bridge be inert? |
So it doesn't react with anything that is present in either half cell |
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Why is a high resistance voltmeter used to measure the voltage? |
It prevents electrons from travelling continuously from one half-cell to another |
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What is the electromotive force? |
The maximum potential difference which the cell can produce |
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What happens when there's a bigger difference between two forces between the high resistance voltmeter? |
Bigger the difference between the two forces, bigger the potential difference and bigger the voltage |
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In a cell diagram, which direction do electrons flow? |
From left to right, from negative electrode to positive electrode |
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What go on the outside of the cell diagram? |
The most reduced form (ROOR) |
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What is the reference electrode? |
Standard hydrogen electrode with electrode potential of zero |
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What is the purpose of platinum in the half cell? |
Allows electron flow as hydrogen doesn't conduct |
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Hydrogen half cell |
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What are the conditions of the standard hydrogen electrode? |
100Kpa 298 Kelvin 1.00 mol dm-³
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What is the benefit of platinum? |
Inert so doesn't react with ions in solution and is a good electrical conducter |
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What is the significance of the e cell value being negative? |
The reaction is not thermodynamically feasible. Only reactions with a positive cell will occur spontaneously. |
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What makes the species on the right a better reducing agent? |
The more negative the e cell value i.e. the more it wants to lose electrons |
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What makes the species on the left a better oxidizing agent? |
The more positive the e cell value i.e. the more it wants to gain electrons |
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In a spontaneous reaction, what happens to the most negative e cell value? |
Reverses direction |
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Which half cell is written on the left? |
The most negative e cell value |
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How is no state change shown in a cell diagram? |
A comma rather than a line |
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What is the EMF value? |
The difference between electrode potentials of the two half cells |
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E cell = |
RHS - LHS |
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If the concentration of reactants is increased, what happens to equilibrium and e cell value? |
Equilibrium shifts to the right and e cell value increases |
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If the concentration of products is increased, what happens to equilibrium and e cell value? |
Equilibrium shifts to the left and E cell for the half cell decreases |
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What can REDOX reactions do? |
Generate the electrical current |
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What is a non-rechargeable cell? |
Primary cells that can only be used once |
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What is a rechargeable cell? |
Secondary cell that can be recharged and reused |
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What is a lithium ion cell? |
Used in mobile phones and laptops Anode : lithium cobalt oxide (Li+[CoO2]-) Cathode : carbon (graphite) |
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How can a cell be recharged? |
Reversing cell reactions by applying an external voltage to drive electrons in the opposite direction |
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What does a fuel cell do? |
Converts chemical energy into electrical energy in a similar fashion to a battery in an open system where reactants flow in and products flow out |
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What do commercial cells use? |
Porous platinum electrodes in constant with concentrated aqueous potassium hydroxide to increase surface area so reaction is faster |
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Why are hydrogen fuel cells not necessarily carbon neutral? |
Processes used to produce hydrogen can be such as electricity from fossil fuels for electrolysis and CO2 in combustion |
