The oxidising agent takes electrons from the species being oxidised; it is the species that is reduced in the reaction.
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Can you construct redox equations from half-equations or oxidation numbers?
See A Level textbook, page 109-110.
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How do you carry out a Manganate (VII) (Fe 2+ / MnO4 -) titration?
Normal self-indicating titration; the manganate decolourises as it is added.
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What is the end point of this titration?
The end point is when a permanent pink colour is formed.
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How do you carry out an iodine (I2 / S2O3 2-) titration?
Normal titration; KI and an oxidising agent react to produce iodine which is a yellow-brown colour, during the titration the iodine is reduced to I- iand the brown colour fades.
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What is the end point of the titration?
When the end point is being approached, the iodine colour fades to pale yellow, and starch indicator is added forming a blue-black colour; the end point is when the blue-black colour disappears.
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Can you complete titration calculations for both reactions?
See A Level textbook pages 113-120.
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What does standard electrode potential mean?
The voltage of a half-cell compared to the standard hydrogen half-cell, under standard conditions.
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How can metals or non-metals in contact with there ions in aqueous solution form a half-cell?
The metal ion must have a concentration of 1 mol dm -3; at the phase boundary (where the metal is in contact with its ions) the equilibrium is set up; when two half-cells are connected, electrons will flow.
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What is an ion / ion half-cell?
Contains ions of the same element in different oxidation states; in this type of half-cell there is no metal to transport electrons either into or out of the half-cell, so an inert platinum electrode is used.
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What is the negative electrode in an operating cell?
The electrode with more reactive metal, which loses electrons and is oxidised.
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How can you calculate the standard cell potential from standard electrode potentials?
E cell = E (positive electrode) - E (negative electrode).
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How do you form an overall equation from two half-equations?
The equation with the most negative value (the oxidation half-equation) is reversed.
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What are the limitations of using E values to make predictions about feasibility?
Reaction Rate - reactions that have a large activation energy will have a very slow rate; Concentration - standard electrode potential use 1 mol dm -3 but many reactions use other concentrations, so will not have the standard electrode potential.
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contd...
Other Factors - the actual conditions used in the reaction may be different from standard conditions, standard electrode potentials apply to aqueous equilibria.
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What are primary cells?
Non-rechargeable cells; when they are used, electrical energy is produced by oxidation and reduction at the electrodes, but the reaction cannot be reversed, so eventually the chemicals will be used up.
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What are secondary cells?
Rechargeable cells; the cell reaction which produces electrical energy can be reversed during recharging.
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How does a fuel cell create a voltage?
A fuel cell uses the energy from the reaction of a fuel with oxygen to create a voltage; the fuel and oxygen flow into the fuel cell and the products flow out, so the electrolyte stays in the cell.
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Why are hydrogen fuel cells sustainable?
They don't produce carbon dioxide during combustion, water is the only waste product.
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Other cards in this set
Card 2
Front
Can you construct redox equations from half-equations or oxidation numbers?
Back
See A Level textbook, page 109-110.
Card 3
Front
How do you carry out a Manganate (VII) (Fe 2+ / MnO4 -) titration?
Back
Card 4
Front
What is the end point of this titration?
Back
Card 5
Front
How do you carry out an iodine (I2 / S2O3 2-) titration?
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