Chemical Changes Flashcards
(22 cards)
In electrolysis, what is aluminium extracted from?
Bauxite
Why can’t ionic solids be used for electrolysis?
They have to be molten so the ions can move
Where to the positive and negative ions go in electrolysis?
Positive -> cathode
Negative -> anode
What happens at each electrode? (In terms of electrons)
Positive metal ions are reduced (gain electrons)
Negative ions are oxidised (lose electrons)
When do we use electrolysis?
When an element is too reactive to be reduced with carbon
What is aluminium oxide mixed with and why?
Cryolite
Aluminium has a high melting point so it is mixed with cryolite to lower melting point
What happens when each element (aluminium and oxygen) go to the electrodes)
Oxygen evaporates as it forms O2 molecules and aluminium sinks
What is the equation for aluminium oxide in electrolysis
2Al2O3 -> 4Al + 3O2
At the anode, what happens when hydrogen ions and metal ions more reactive than hydrogen are present?
Hydrogen gas is formed
What happens if the metal is less reactive than hydrogen?
A layer of pure metal is produced
What happens if halide ions are present at the anode?
Molecules will be formed
What is oxidisation and reduction in terms of electrons?
O - loss
R - gain
What are redox reaction
Oxidisation and reduction happen at the same time
Are displacement reactions redox reactions?
Yes
Acid plus metal equals
Salt plus hydrogen
Metal plus water equals
Metal hydroxide plus hydrogen
Metals less reactive than carbon also don’t react with water true or false
True
Three strong acids
Hydrochloric
Sulfuric
Nitric
Three weak acids
Citric
Carbonic
Ethanoic
What is concentration?
Volume of acid in a given volume
Acid plus base equals
Salt and water
