topic 4 - chemical changes: electrolysis Flashcards
What type of compounds are used in electrolysis?
Ionic.
What happens when an ionic compound is melted or dissolved in water?
They are free to move around the solution.
What is an electrolyte?
A molten or dissolved ionic compound which is able to conduct electricity.
What are the two electrodes?
Anode and cathode.
What happenns when you pass a current through an electrolyte?
The ions move to the electrodes.
What is the anode?
The positively charged electrode.
What is the cathode?
The negatively charged electrode.
What is an anion?
A negatively charged ion.
What is a cation?
A positively charged ion.
Which electrode do positively charged ions move towards?
The cathode (the negatively charged electrode.
Which electrode do negatively charged ions move towards?
The anode (the positively charged electrode.
What happens when ions are discharged at the electrodes?
They produce elements.
What do ions create when they travel to the electrodes?
A flow of charge through the electrolyte.
Why can’t an ionic solid be electrolysed?
Because the ions are in fixed positions and can’t move.
What are molten ionic liquids (e.g. lead bromide) always broken up into?
Their elements.
In the electrolysis of molten ionic compounds, what is produced at the anode?
The non-metal.
In the electrolysis of molten ionic compounds, what is produced at the cathode?
The metal.
When is electrolysis used to extract metals from their ores?
When the metal is too reactive to be extracted by reduction with carbon or if the metal reacts with carbon.
What is a disadvantage of extracting metals from their ores using electrolysis?
It is very expensive as lots of energy is needed to melt the compounds and produce the electrical current.
How is aluminium manufactured?
By the electrolysis of a molten mixture of aluminium oxide and cryolite using carbon as the positive
electrode (anode).
Why is a mixture used as the electrolyte in the extraction of aluminium?
To lower the melting point and therefore make it more cost-effective.
Why must the positive anode be continually replaced in the extraction of aluminium?
The anode is made of carbon which reacts with oxygen to form carbon dioxide.
When you electrolyse an aqueous solution, what else do you have to factor in?
The ions in the water.
In the electrolysis of aqueous solutions, what is produced at the cathode if the metal is more reactive than hydrogen?
Hydrogen gas.
