Oxidation and reduction in terms of oxygen and in terms of electrons, displacement reactions, and writing half equations. Includes Higher tier content.
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1.Define oxidation in terms of oxygen.
The gain of oxygen by a substance.
2.Define reduction in terms of oxygen.
The loss of oxygen from a substance.
3.Define oxidation in terms of electrons.
The loss of electrons.
4.Define reduction in terms of electrons.
The gain of electrons.
5.What mnemonic helps remember this?
OIL RIG: Oxidation Is Loss, Reduction Is Gain, referring to electrons.
6.When magnesium forms Mg2+, is it oxidised or reduced?
Oxidised, because it has lost two electrons.
7.When a chlorine atom forms Cl-, is it oxidised or reduced?
Reduced, because it has gained an electron.
8.What is a redox reaction?
A reaction in which oxidation and reduction happen at the same time.
9.Why must oxidation and reduction always occur together?
Electrons lost by one substance have to be gained by another, so one is always oxidised and the other reduced.
10.What is a displacement reaction?
A reaction in which a more reactive metal takes the place of a less reactive metal in a compound.
11.Will magnesium displace copper from copper sulfate?
Yes. Magnesium is more reactive, so it displaces the copper.
12.What would you observe in that reaction?
The blue solution fades, an orange-brown solid coats the magnesium, and the mixture warms up.
13.Will copper displace magnesium from magnesium sulfate?
No. Copper is less reactive than magnesium, so nothing happens.
14.In a displacement reaction, which metal is oxidised?
The more reactive metal, because it loses electrons to form ions.
15.In a displacement reaction, which metal ion is reduced?
The less reactive metal ion, because it gains electrons to become the metal atom.
16.What is a half equation?
An equation showing what happens to just one substance, including the electrons lost or gained.
17.Write the half equation for magnesium forming its ion.
Mg gives Mg2+ + 2e-
18.Write the half equation for copper ions becoming copper.
Cu2+ + 2e- gives Cu
19.How do you know a half equation is balanced?
The atoms must balance and the total charge must be the same on both sides.
20.Write the half equation for a chloride ion forming chlorine gas.
2Cl- gives Cl2 + 2e-
21.In Zn + CuSO4 gives ZnSO4 + Cu, what is oxidised?
The zinc, because it loses electrons to become Zn2+.
22.What is a spectator ion?
An ion that is present but does not change during the reaction, such as the sulfate ion in a displacement reaction.
23.Why is extracting a metal from its oxide described as reduction?
The metal compound loses its oxygen, and the metal ions gain electrons to become metal atoms.
24.Is a metal reacting with acid a redox reaction?
Yes. The metal loses electrons and is oxidised, while hydrogen ions gain electrons and are reduced to hydrogen gas.
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