AQA Combined Chemistry 5.4 Flashcards
Revision for Paper 1
Why is cryolite used in the electrolysis of aluminium oxide?
To lower the melting point of aluminium oxide (to save energy and costs)
In the electrolyis of lead bromine, what collects at:
a) the posistive electrode (the anode)?
b) the negative electrode (the cathode)?
a) Bromine
b) Lead
To which electrod are negative ions attracted to?
Positive electrode
In electrolysis, what is the negative electrode called?
Cathode
To which electrode are positive ions attracted to?
Negative electrode
In electrolysis what is the positive electrode called?
Anode
What is the pH range of acids?
0-6
What is the pH range for alkalis?
8-14
What is the pH of a neutral solution?
7
Name the ‘salt’ produced when the following chemicals react:
a) Sodium carbonate + nitric acide
b) Magnesium oxide + sulfuric acid
c) Iron hydroxide + hydrochloric acid
a) Sodium nitrate
b) Magnesium sulfate
c) Iron chloride
Write the formulae of the following salts using the formulae of ions provided below:
a) Sodium Chloride
b) Magnesium Chloride
a) NaCl
b) MgCl2
What type of reaction is shown by the equation below?
magnesium + oxygen - magnesium oxide
Oxidation
What is the name for the reaction the gaining of oxygen?
Oxidation
What 2 non-metlas are often included in the reactivity series?
Hydrogen and Carbon
What is the name for the reaction that involves the removal of oxygen?
Reduction
Put the following elemetnts in order of reactivity from least to most reactive:
iron / lithium / zinc / copper / potassium / calcium / sodium / magnesium
copper - iron - zinc - magnesium - calcium - lithium - sodium - potassium
What chemical reaction is shown by the equation below to extract iron from iron oxide?
Iron oxide + carbon - iron + carbon dioxide
Reduction
What type of seperation process would you use to seperate a soluble salt?
Crystallisation
What type of seperation process would you use to seperate an insoluble salt?
Filtration
Why must aluminium be extracted by electrolysis?
It is more reactive than carbon
Why does the positive electrode have to be regularly replaced in the extraction of aluminium oxide?
Because oxide ions react with the carbon electrode
Releasing CO2
Meaning the electrodes gradually degrade
Write an ionic equation for each of teh displacement reactions below:
a) Mg + CuSO4 - Cu + MgSO4
b) Fe + CuCl2 - Cu + FeCl2
a) Mg (s) + Cu2+ (aq) - Cu (s) + Mg2+ (aq)
b) Fe (s) + Cu2+ (aq) - Cu (s) + Fe2+ (aq)
In the following equation, state which species are oxidised and which are reduced?
Mg (s) + 2HCl (aq) - MgCl2 (aq) + H2 (g)
- Magnesium atoms are oxidised
- Hydrogen atoms are reduced
Fill in the blanks:
a) Oxidation is the _____ of electrons
b) Reduction is the _____ of electrons
a) loss
b) gain
In the following equation, state which species are oxidised and which are reduced?
2Fe2O3 + 3C - 4Fe + 3CO2
- 2Fe2O3 is reduced
- 3C is oxidised
During electrolysis, what happens to ions at the:
a) Cathode?
b) Anode?
a) Ions gain electrons and turn into atoms (reduction)
b) Ions lose electrons and turn into atoms (oxidation)
Write half equations at the anode and cathode for the electrolysis of water
- Anode: 4OH- — 4e- = O2 + 2H2O
- Cathode: 2H+ ++ 2e- = H2
Explain why the reaction below is a redox reaction
Zn (s) + 2HCl (aq) - ZnCl2 (aq) + H2 (g)
- Zinc atoms are oxidised
- Hydrogem atoms are reduced
- Hence reduction and oxidation happen at the same time so it’s called a redox reaction
Write the half equations at the anode and cathode for the electrolysis of lead bromide
- Anode: 2Br- – 2e- = Br2
- Cathode: Pb2+ ++ 2e- = Pb
As the hydrogen ion concentration of a solution increases by a factor of 10, what happens to the pH of the solution?
The pH decreases by 1 unit
If you compared the pH of a 1M Strong Acid and a 1M Weak Acid, which would have a high pH and why?
The weaker acid will have the higher pH because it only partially ionises in water
What is a ‘weak’ acid?
An acid that is only partially ionised in water
Give 2 examples of strong acids and 2 examples of weak acids
Strong acids include: Hydrochloric, Nitric and Sulfuric
Weak acids include: Carbonic, Ethanoic and Citric
Name the ion found in acidic solutions
Hydrogen ion, H+
Name the ion found in alkaline solutions
Hydroxide ion, OH-
Write an ionic equation for neutralisation
H+ (aq) + OH- (aq) = H2) (l)
Why does a metal compound have to be molten or dissolved for electrolysis to work?
Because the ions need to be free to flow
What is the name for the reaction when an acid reacts with an alkali to make a salt + water?
Neutralisation reaction
When there are several ions in solution, which ion will collect:
a) at the anode?
b) at the cathode?
a) Hydrogen is produced if the metal is more reactive than Hydrogen
b) Oxygen is produced unless the solution contains halide ions, then the halogen is produced
What is the name for the liquid that contains the ions the electrolysis process?
Electrolyte
Why is gold found naturally in the Earth, but other metals are locked up in compounds?
Gold is unreactive
Describe how you would make a pure, dry sample of a soluble salt using an insoluble base and an acid
- add base in excess to acid
- filter excess base
- crystallisation; to seperate salt from its solution
If an atom is very reactive, is it more or less likely to turn into an ion?
More likely
Why can’t aluminium be extracted by reduction with carbon?
Aluminium is more reactive than carbon
Complete the general equation:
Metal + Acid - ___ + ___
Metal + Acid - Salt + Hydrogen
Complete the general equation:
Metal + Water - ___ + ___
Metal + Water - Metal hydroxide + Hydrogen
Complete the general equation:
Acid + Metal Carbonate - ____ + _____
Acid + Metal Carbonate - Salt + Water + carbon dioxide
Complete the general equation:
Acid + Metal oxide - ____ + ____
Acid + Metal oxide - Salt + Water
