Electrolysis Flashcards
What happens when you pass an electric current through an ionic substance which is molten?
Brakes them down into elements
E.g. lead bromide or solutions
What happens in electrolysis?
Positively charged ions move to the negative electrode, and negatively charges ions move to the positive electrode
What is electrolysis used for?
To electroplated objects
This may be for a variety of reasons and includes copper plating and silver plating
What happens at the negatively changed electrode?
The positively charged ions gain electrons (reduction)
What happens at the positively charged electrode?
The negatively charged ions lose electrons (oxidation)
If there is a mixture of ions, the products formed depend on:
The activity of the elements involved
How can half equations be represented?
2Cl- (gives you) Cl2 + 2e-
Or
2Cl- -2e- (gives you) Cl2
How is aluminium manufactured?
By electrolysis of a molten mixture of aluminium oxide and cryolite. Aluminium forms at the negative electrode and oxygen at the positive electrode. The positive electrode is made of carbon, which reacts with the oxygen to produce CO2
What does electrolysis of sodium chloride produce?
Hydrogen and chlorine
Sodium hydroxide solution is also produced. These are important reagents for chemical industry, eg sodium hydroxide for the production of soap and chlorine for the production of bleach and plastics
What happens when an ionic substance is melted or dissolved in water?
The ions are free to move about within the liquid or solution
Why is cryolite used in the extraction of aluminium?
Aluminium oxide has a very high melting point, so it would be expensive to melt it. Instead, it is dissolved in cryolite - an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium.
