Electrolysis Flashcards
Electrolysis
break down of compound into its elements using an electric current
Electrolysis is used for
-Extract metals from their metal ores when the metals cannot be extracted by heating their ores with carbon
-Purify metals
-Produce non-metals such as fluorine
Electrolyte
the compound that is broken down during electrolysis and it is either a molten ionic compound or a concentrated aqueous solution of ions
Anode
the positive electrode
Cathode
the negative electrode
Electrolysis of molten electrolytes
-Cations (positively charged ions) move to the negatively charged cathode where they gain electrons
-Reduction takes place at the cathode
-If a metal is formed, a layer of metal is deposited on a cathode or it forms a molten layer in the cell
-If hydrogen gas is formed, bubbles are seen
-Anions (negatively charged ions) move to the positively charged anode where they lose electrons
-Oxidation takes place at the anode
Electrolysis of aqueous solutions
-Aqueous solutions have more than one cation and anion in solution due to the presence of water
-The actual ions that are discharged during electrolysis will depend on:
1)The relative electrode potential of the ions
2)The concentration of the ions
-The positively charged cation with the most positive Eꝋ will be discharged at the cathode as this is the cation that is most easily reduced
-The negatively charged anion with the most negative Eꝋ will be discharged at the anode, as this is the anion that is most easily oxidised
How electrode potential of ion effects electrolysis in aqueous solutions
-The positively charged cation with the most positive Eꝋ will be discharged at the cathode as this is the cation that is most easily reduced
-The negatively charged anion with the most negative Eꝋ will be discharged at the anode, as this is the anion that is most easily oxidised
How concentration of ions effects electrolysis in aqueous solutions
Ions that are present in higher concentrations are more likely to be discharged
Relative electrode potential of ions
how easily an ion is discharged during electrolysis
The amount of substance that is formed at an electrode during electrolysis is proportional to:
-The amount of time where a constant current to passes
-The amount of electricity, in coulombs, that passes through the electrolyte (strength of electric current)
Q =
I x t
One faraday is
-the amount of electric charge carried by 1 mole of electrons or 1 mole of singly charged ions
-96 500 C mol-1
F =
L x e
Avogadro’s constant (L)
number of entities in one mole
