Electrolytic Process Flashcards
Describe the reactions at the electrodes.
At the cathode electrons are transferred from the electrode to the positive ions at the an ode negative ions lose electrons. When positive ions gain electrons we call it reduction.
What is an electrolyte
Something that conducts electricity it is used in electrolysis
In molten electrolysis describe how metals and there partner are formed I.e sodium chloride
Oxidation is the loss of electrons reduction is the addition of electrons.
At the Anode negative ions are attracted to it, these ions are then oxidised as they are negative they then form an atom I.e Cl- to Cl2
At the cathode electrons from the anode are used to reduce the positive atoms I.e Na+ + E- to Na
Why is copper always formed at the cathode?
Because copper is positive therefore attracts to the negative anode where is it reduced.
What happens in electrolysis when water is used as the solute and the salt is dissolved
If the salt is more reactive than hydrogen it will form at the cathode however if it is less reactive then water it will form at the bottom of the container and the hydrogen will be found at the cathode.
Describe advantages of electro plating
Makes things look nicer, I.e gold plating
Prevents corrosion
What in the electrolyte conduct electricity
Free ions
What is an electrolyte
It is an ionic substance
What half equations happen at the cathode and the anode of molten sodium chloride . Cl- and Na+
Cathode - Na+ + e- to Na
Anode - 2Cl - to Cl2 plus 2 e-
Which ions are attracted to which electrodes
The anion is attracted to the anode because the anion is negative the anode is positive. The cation is attracted to the cathode as the cation is positive and is attracted to the negative cathode
What is oxidation and where does it occur
It is the loss of electrons so occurs at the anode where negative ions loose electrons
What is reduction and where does it happen
It is gaining of electrons so occurs at the cathode because the cations are positive they need electrons . Na+ + E- to Na
What are the half equations for molten lead bromide Pb2+
Br-
Cathode Pb2+ + 2e- to Pb
Anode 2Br- to Br2 plus 2e-, there are two bromide reactants as it forms a diatomic molecule
Why is electrolysis of solutions different to molten substances
Molten ionic salts only contain the ions of that salt. But solutions also have H+ and OH- ions from the water
In electrolysis of solutions which ion is discharged at the anode
The simplest one, for example Cl is discharged instead of OH and OH is discharged instead of SO4
What happens at the cathode in electrolysis of solutions
The metal will be discharged if it’s less reactive than hydrogen . For example copper is less reactive than hydrogen so is discharged in electrolysis of copper salts. But sodium is more reactive than hydrogen so hydrogen will be discarded for sodium salts and the sodium will collect at the bottom
What’s the half equation for hydroxide discharging at the anode
40H- to 2H20 + 02 + 4e-
How can you purify copper
By electrolysis
Where does impure copper start in electrolysis
The anode it
What is used for the cathode in copper purification
Pure copper
Describe how copper if purified
Electrons are pulled of the atoms at the anode they go into solution as Cu2+ ions. At the cathode they gain electrons and become Cu . Impurities at the anode are dropped as sludge.
What happens at the anode in copper sulfate purifation
Copper atoms dissolve form the impure anode
Cu -> Cu2+ + 2e-
How can you show that copper atoms are moving from anode to cathode
Weigh the anode and cathode before the electrolysis and weigh them after
What is electroplating
The process of coating a metal with another metal using electricity
Which electrode is the object you want to plate
Usually the cathode
Why electroplate
For jewellery improves the appearance making them shinty and attractive. To prevent corrosion. Some cutlery is electroplated as it is iron and the stops it oxidising with oxygen
