Chemical Changes Flashcards
What is oxidation/reduction?
Oxidation - When a substance gains oxygen
Reduction - When a substance loses oxygen
What is the reactivity series of metals?
The series shows the metals in order of their reactivity.
What are the trends in
reactivities of metals in reactions with acids/water?
Metals above H2
in reactivity series react with acid to produce H2
. The more
reactive the metal is, the quicker and more violent reaction with acid occurs.
Metals below H2
don’t react with acids.
Not all metals above H2
react with water - mostly Group I and II metals. Aluminium
is the borderline case.
What is a displacement reaction?
A reaction where a more reactive metal displaces a less reactive metal from a
compound
How are unreactive metals found in Earth?
In their natural state
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 a reaction between metals
and acids?
Metal + acid → salt + hydrogen
Which metals in the reactivity series will react with acid?
Those above hydrogen
What is the general equation for a neutralisation reaction?
Base + acid → salt + water
What is a redox reaction?
A reaction where both oxidation and reduction occurs
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 and alkalis produce in aqueous solutions
Acids produce hydrogen ions, alkalis produce hydroxide ions
What are bases, acids and alkalis?
Bases are compounds that neutralise acids, acids produce hydrogen ions in
aqueous solutions, alkalis are soluble bases - produce hydroxide ions in aqueous
solutions
What is a strong acid and weak acid?
Strong acid is completely ionised in aqueous solution; weak acid is only partially
ionised in aqueous solution
Name the following salts: LiNO3
, K2CO3
, MgBr2
,
BaSO4
Lithium nitrate
Potassium carbonate
Magnesium bromide
Barium sulphate
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 is a cathode and what is an anode?
Cathode is the negative electrode, anode is the positive electrode
How is aluminium manufactured? Why is it expensive?
Aluminium is made through the electrolysis of aluminium oxide and cryolite.
Lots of energy is needed to produce the current in electrolysis which makes this
process expensive.
What are the half equations in the extraction of aluminium?
Al3+ + 3 e−
→ Al (cathode)
2 O2− → O2
+ 4 e− (anode)
Oxygen reacts with C of the anode producing CO2
.
Why is cryolite used in manufacturing of aluminium?
It lowers the melting point of aluminium oxide, reducing energy costs
What are the half equations in electrolysis of the
aqueous Na2SO4
?
2 H+
+ 2 e−
→ H2
(cathode)
4 OH−
→ 2 H2O + O2
+ 4 e− (anode)
What are the half equations in electrolysis of the
molten and aqueous KCl?
K
+
+ e−
→ K (cathode)
2 Cl−
→ Cl2
+ 2 e− (anode)
2 H+
+ 2 e−
→ H2
(cathode)
2 O2− → O2
+ 4 e− (anode)
What are the half equations in electrolysis of the
aqueous CuBr2
?
Cu2+ + 2 e−
→ Cu (cathode)
2 Br−
→ Br2
+ 2 e− (anode)
