4 Chemical Changes - Electrolysis Flashcards
What is electrolysis?
Using electricity to break down a substance
What happens to an ionic substance when it is melted or dissolved in water?
The ions become free to move around
What is the name for the positive electrode?
The anode
What is the name for the negative anode?
The cathode
Do positive ions move to the anode or the cathode?
Cathode
Do negative ions move to the anode or the cathode?
Anode
At which electrode would Zn2+(aq) turn into Zn(s)?
Cathode (needs to gain electrons)
At which electrode would Cl-(aq) turn into Cl2(g)?
Anode (needs to lose electrons)
Balance the equation: Al3+ + e- gives Al
Al3+ + 3e- gives Al
Balance the equation: Cl- gives Cl2 + e-
2Cl- gives Cl2 + 2e-
Balance the equation: O2- gives O2 + e-
2O2- gives O2 + 4e-
What will be the products for the electrolysis of molten iron bromide?
Iron and bromine
What will be the products for the electrolysis of molten zinc oxide?
Zinc and oxygen
For the extraction of which metals is electrolysis needed?
Ones more reactive than carbon, e.g. aluminium
What are the two main disadvantages of using electrolysis to extract metals?
Requires a large amount of energy to melt the compounds and to produce the necessary electricity
Why is aluminium oxide mixed with cryolite when extracting aluminium?
To lower the melting point
What is produced at the anode and cathode in the electrolysis of aluminium oxide?
Aluminium at the cathode and oxygen at the anode
Why does the anode need to be replaced in the electrolysis of aluminium oxide?
The oxygen reacts with the carbon electrode to produce carbon dioxide.
In the electrolysis of sodium chloride solution, what are the products?
Chlorine gas and hydrogen gas
Why is sodium not produced in the electrolysis of sodium chloride solution?
It is more reactive than hydrogen so hydrogen is produced instead.
What is produced at the anode in electrolysis of solutions?
Either a halogen or oxygen (when there is no halogen present)
