Combined Chemistry - C4 Chemical Changes Flashcards
What two non-metals are often included in the reactivity series?
Hydrogen and Carbon
What is the name for the reaction that involves the gaining of oxygen?
Oxidation
If an atom is very reactive, is it more or less likely to turn into an ion?
More likely
What type of reaction is shown by the equation below?
magnesium + oxygen → magnesium oxide
Oxidation
What is that name for the reaction that involves the removal of oxygen?
Reduction
Put the following elements in order of reactivity from least to most reactive:
iron / lithium / zinc / copper / potassium / calcium / sodium / magnesium
(least reactive) copper – iron – zinc – magnesium – calcium – lithium – sodium – potassium (most reactive)
Why can’t aluminium be extracted by reduction with carbon?
Aluminium is more reactive than carbon
What chemical reaction is shown by the equation below to extract iron from iron oxide?
Iron oxide + carbon → iron + carbon dioxide
Reduction (with carbon)
Q. Complete the general equation:
Metal + Acid →
Q. Complete the general equation:
Metal + Water →
- Metal + Acid → Salt + Hydrogen
- Metal + Water → Metal hydroxide + Hydrogen
Q. Complete the general equation:
Acid + Metal Carbonate →
Q. Complete the general equation:
Acid + Metal oxide →
Acid + Metal carbonate → Salt + Water + Carbon dioxide
Acid + Metal oxide → Salt + Water
What type of separation process would you use to separate a soluble salt?
Crystallisation
What type of separation process would you use to separate an insoluble salt?
Filtration
Why is gold found naturally in the Earth, but other metals are locked up in compounds?
Gold is unreactive
Name the ‘salt’ produced when the following chemicals react:
a) Sodium carbonate + nitric acid
b) Magnesium oxide + sulfuric acid
c) Iron hydroxide + hydrochloric acid
*these are just examples, you need to be able to do this for any base reacting with hydrochloric, sulfuric and nitric acid.
a) Sodium nitrate
b) Magnesium sulfate
c) Iron chloride
Write the formulae of the following salts using the formulae of ions provided below.
Formulae of common ions: Na+, Cl-, Mg2+
a) Sodium Chloride
b) Magnesium Chloride
*these are just examples, you need to be able to do this for any salt when given the formulae of common ions
a) NaCl
b) MgCl2
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 separate salt from its solution.
a) What is the pH range of acids?
b) What is the pH range of alkalis?
c) What is the pH of a neutral solution?
a) 0-6
b) 8-14
c) 7
Name the ion found in alkaline solutions
Hydroxide ion, OH-
Write an ionic equation for neutralisation
H+ (aq) + OH- (aq) → H2O (l)
What is the name for the separation process shown in the diagram?
Electrolysis
Name the ion found in acidic solutions
Hydrogen ion, H+
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) At the cathode: Hydrogen is produced if the metal is more reactive than Hydrogen
b) At the anode: 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 in the electrolysis process?
Electrolyte
In electrolysis, what is the positive electrode called?
Anode
To which electrode are positive ions attracted to?
Negative electrode (opposites attract)
In the electrolysis of lead bromide, what collects at:
a) The positive electrode (the anode)?
b) The negative electrode (the cathode)?
- Bromine (at the anode)
- Lead (at the cathode)
Why must aluminium be extracted by electrolysis?
It is more reactive than carbon (and therefore can’t be extracted by reduction with carbon)
In electrolysis, what is the negative electrode called?
Cathode
To which electrode are negative ions attracted to?
Positive electrode (opposites attract)
Why does a metal compound have to be molten or dissolved for electrolysis to work?
Because the ions need to be free to flow
Why is cryolite used in the electrolysis of aluminium oxide?
To lower the melting point of aluminium oxide (to save energy and costs)
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
Higher Q. Fill in the blanks:
Oxidation is the _____ of electrons.
Reduction is the _____ of electrons.
- Oxidation is the loss of electrons
- Reduction is the gain of electrons
Higher Q. In the following equation, state which species are oxidised and which are reduced?
2Fe2O3 + 3C → 4Fe + 3CO2
*this is just an example, you need to be able to do this for any given reaction.
- 2Fe2O3 (Iron oxide) is reduced
- 3C (carbon) is oxidised
Higher Q. Explain why the reaction below is a redox reaction.
Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)
- Zinc atoms are oxidised.
- Hydrogen atoms are reduced.
- Hence reduction and oxidation happen at the same time so it’s called a redox reaction.
Higher Q. Write an ionic equation for each of the displacement reactions below:
a) Mg + CuSO4 → Cu + MgSO4
b) Fe + CuCl2 → Cu + FeCl2
*these are just examples, you need to be able to do this for any displacement reaction.
a) Mg(s) + Cu2+(aq)→ Cu(s) + Mg2+(aq)
b) Fe(s) + Cu2+(aq) → Cu(s) + Fe2+ (aq)
Higher Q. In the following equation, state which species are oxidised and which are reduced?
a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)
*this is just an example, you need to be able to do this for reactions between the following metals (magnesium, zinc, iron) and the following acids (hydrochloric and sulfuric)
- Magnesium atoms (Mg) are oxidised.
- Hydrogen ions (H+) are reduced.
Higher Q. During electrolysis, what happens to ions at the:
a) Cathode?
b) Anode?
- At the Cathode: Ions gain electrons and turn into atoms (Reduction)
- At the Anode: Ions lose electrons and turn into atoms (Oxidation)
Higher Q. Write half equations at the anode and cathode for the electrolysis of water.
Anode: 4OH- - 4e- → O2 + 2H2O
or 4OH- → O2 + 2H2O + 4e-
Cathode: 2H+ + 2e- → H2
Higher Q. Give two examples of strong acids and two examples of weak acids.
- Strong acids include: Hydrochloric, Nitric and Sulfuric
- Weak acids include: Carbonic, Ethanoic and Citric
Higher Q. What is a ‘weak’ acid?
An acid that is only partially ionised in water
Higher Q. If you compared the pH of a 1M Strong Acid and a 1M Weak acid, which would have the higher pH and why?
The weaker acid will have the higher pH because it only partially ionises in water (or vice versa).
Higher Q. 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
Higher Q. Write the half equations at the anode and cathode for the electrolysis of lead bromide.
*this is just an example, you need to be able to do this for any given electrolysis example.
Anode: 2Br- - 2e- → Br2 or 2Br- → Br2 + 2e-
Cathode: Pb2+ + 2e- → Pb
