Anita Akweshie-
definition of electrolysis
the breaking own of a compound into its elements using an elements using an electric current
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what is electrolysis often used for
extract metals from their metal ores
purify metals
produce non-metals
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what is the circumstance under which metals are extracted electrolysis
when metals cannot be extracted by heating their ores with carbon
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what is electrolysis carried out in
an electrolysis cell
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what does an electrolysis cell consist of
an electrolyte
2 electrodes
power supply
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what is an electrolyte
the compound that is broken down during electrolysis, either a molten ionic compound or a concentrated aqueous solution of ions
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what are electrodes
metal or graphite rods that conduct electricity to and away from the electrolyte
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the positive electrode
anode
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the negative electrode
cathode
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what kind of current must the power supply of the electrolysis cell have
direct
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where cations gain electrons
negatively charged cathode
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which redox reaction takes place at the cathode
reduction
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what happens when a metal is formed at the cathode
metal deposited on the cathode
forms a molten layer
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observation when hydrogen gas is formed at the cathode
bubbles are seen
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where anions lose electrons
positively charged anode
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which redox reaction takes place at the anode
oxidation
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true/false
aqueous solutions have more than one cation and anion in solution due to the presence of water
true
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which ions does water contribute to a solution
H+ and OH-
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why does water splits into H+ and OH- during electrolysis
it is a weak electrolyte
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what the actual ions that are discharged during electrolysis depend on
the relative electrode potential of the ions
the concentration of ions
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what is the relative electrode potential of ions
describes how easily an ion is discharged during electrolysis
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what property must a positively charged cation have tobe discharged first at the cathode
the most positive relative electrode potential
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why will the the positively charged cation with the most positive electrode potential be discharged first
it is the most easily reduced
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when working with a concentrated aqueous solution of NaF, what will be discharged at the cathode and why
H+ ions because they have a higher relative electrode potential the Na+
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what property must the negatively charged anion have to be discharged from anode first
the most negative relative electrode potential
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why must the anion have the most negative relative electrode potential in order to be discharged first from the anode
it is most easily oxidised
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when working with a concentrated aqueous solution of NaF, what anions will be discharged first at the anode and why?
F- since they have a lower relative electrode potential than OH-
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during electrolysis what influences the likelihood of discharge of ions at the electrodes
the concentration of ions as they are proportional
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when working with a concentrated solution of NaF during electrolysis, why are more (mainly) fluoride ions discharged at the anode
fluoride ions are in higher concentration
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when working with a very dilute solution of NaF during electrolysis, why will a mixture of both oxygen and fluorine gas be formed at the anode
there is much more oxygen and much less fluorine available
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what type of reaction is electrolysis
a redox reaction
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what must always balance when writing electrolysis equations from both electrodes
electrons
