C4- Chemical Changes Flashcards
What is oxidation?
Oxidation is when a substance gains oxygen.
What is reduction?
Reduction is when a substance loses oxygen.
What is the reactivity series of metals?
The series shows the metals in order of their reactivity.
What happens to metals above hydrogen in the reactivity series when they react with acids?
They react with acid to produce hydrogen gas. The more reactive the metal, the quicker and more violent the reaction.
Do metals below hydrogen react with acids?
No, metals below hydrogen do not react with acids.
Do all metals above hydrogen react with water?
Not all metals above hydrogen react with water; mostly Group I and II metals do. Aluminium is a borderline case.
What is a displacement reaction?
A reaction where a more reactive metal displaces a less reactive metal from a compound.
How can metals less reactive than carbon be extracted?
Reduction with carbon. Carbon displaces the metal in a metal oxide - gets oxidised to carbon oxides. Metal from the metal oxide gets reduced to the pure metal.
How are oxidation and reduction defined in terms of electron transfer?
oxidation – loss of electrons
reduction – gain of electrons
What is the general equation for the reaction between metal carbonate and acid?
Metal carbonate + acid → salt + water + carbon dioxide
What is the general equation for the reaction between metal oxides and acids?
Metal oxide + acid → a salt + water
How is a soluble salt formed?
a) React the excess acid with some insoluble chemical (e.g. metal oxide)
b) Filter off the leftovers
c) Crystallise the product
What do acids produce in aqueous solutions?
Acids produce hydrogen ions.
What do alkalis produce in aqueous solutions?
Alkalis produce hydroxide ions.
What is the general equation for a neutralisation reaction in a short, ionic form?
H+ + OH → H2O
What is electrolysis?
The passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these.
What is an electrolyte?
The liquid/solution which conducts electricity
What occurs at the cathode during electrolysis?
Reduction occurs at the cathode
What occurs at the anode during electrolysis?
Oxidation occurs at the anode
In aqueous electrolysis, which element is discharged at the cathode?
The less reactive element discharges at the cathode. Hydrogen is produced unless there is a less reactive metal in which case the said metal is produced.
Oxygen is produced at the anode unless what?
Oxygen is produced at the anode unless the solution contains high ions, in which case halogen molecules are produced.
How is aluminium manufactured?
Aluminium is made through the electrolysis of aluminium oxide and cryolite.
Why is aluminium expensive?
Lots of energy is needed to produce the current in electrolysis, which makes this process expensive.
Why is cryolite used in manufacturing of aluminium?
It lowers the melting point of aluminium oxide reducing energy costs
