Electrolysis Flashcards
(33 cards)
Why can’t solid compounds conduct electricity?
The ions are locked in place by strong electrostatic forces of attraction, so aren’t free to move about
Why can compounds conduct electricity in water?
The strong electrostatic forces of attraction are broken when melted or dissolved in water. Therefore, the ions are free to move and carry charge to conduct electricity.
Describe the process of electrolysis
when an ionic compound is dissolved in water, the ions become free to move about within the liquid or solution.
these solutions can conduct electricity
passing an electric current through electrolytes causes the ions to move towards the electrodes.
positively charged ions move to the cathode
negatively charged ions move to the anode
ions are discharged at the electrodes producing elements
What is electrolysis?
The decomposition of a compound using an electric current
What happens during electrolysis of molten ionic compounds?
A metal is produced at the cathode and a non-metal is produced at the anode.
Why might metals be extracted from molten compounds using electrolysis?
If the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon
what are the disadvantages of using electrolysis to extract metals from their ores?
its very expensive as lots of energy is required to melt the ore and produce the required current
what is the ore from aluminum oxide?
bauxite
how is aluminum oxide extracted from bauxite?
by electrolysis
why is aluminium mixed with cryolite?
to lower the melting point
why will the molten mixture conduct electricity?
it contains free ions
describe the formation of aluminium by electrolysis
aluminium is extracted from the ore bauxite by electrolysis
aluminium oxide is mixed with cryolite to lower the melting point
the positive aluminium ions are attracted to the negative electrode where they each pick up three electrons and turn into neutral aluminium atoms.
they sink to the bottom of the electrolysis tank
the negative oxygen ions are attracted to the positive electrode where they lose two electrons.
the neutral oxygen atoms will then combine to from oxygen molecules
what happens when a simple ionic compound is electrolysed?
the metal is produced at the cathode and the non metal is produced at the cathode
eg lead bromide
lead is produced at the cathode and bromine is produced at the anode
explain why a mixture is used as the electrolyte?
the molten mixture contains free ions so it will conduct electricity
explain why the positive electrode must be continually replaced
it is made form carbon so reacts with oxygen to produce carbon dioxide
In aqueous solutions, what ions are there not including the ions from the ionic compound?
Hydrogen ions (H+) and hydroxide ions (OH-) from the water.
what is produced at the cathode? (aqueous solution)
hydrogen if the metal is more reactive than hydrogen
what is produced at the anode? (aqueous solution)
oxygen unless the solution contains halide ions when the halogen is produced
why does this happen?
this happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are discharged
what happens at the cathode during electrolysis?
positively charged ions gain electrons
what happens at the anode during electrolysis?
negatively charged ions lose electrons
give an example of a half equation
2H+ +2e- —>H2
test for hydrogen
‘squeaky pop’ with lit splint
test for chlorine
litmus paper
(bleaches it, turning it white)
