Ionisation of elements
Ionisation of Group 1 elements (alkaline metals)
Atoms of Group 1 elements have 1 electron in the outer shell, so they ionise by losing 1 electron to form a positively charged ion of charge +1. This is oxidation because it involves loss of electrons.
Sodium → sodium ion + electron
Na → Na+ + e–
Ionisation of Group 2 elements (alkaline earth metals)
Atoms of Group 2 elements have 2 electrons in the outer shell, so they ionise by losing 2 electrons to form a positively charged ion of charge +2. This is oxidation because it involves loss of electrons.
Magnesium → magnesium ion + 2 electron
Mg → Mg2+ + 2e–
Ionisation of Group 7 elements (halogens)
Atoms of Group 7 elements have 7 electrons in the outer shell, so they ionise by gaining 1 electrons to form a negatively charged ion of charge -1. This is reduction because it involves gain of electrons.
Chlorine + electron → chlorine ion
Cl2 + 2e– → 2Cl–
Reactions involving acids
Reactions of metals with acids
Reactive metals react with dilute acids to form a salt and hydrogen gas.
Magnesium + sulphuric acid → magnesium sulphate + hydrogen
Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)
Zinc + hydrochloric acid → zinc chloride + hydrogen
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Magnesium + nitric acid → magnesium nitrate + hydrogen
Mg(s) + HNO3(aq) → Mg(NO3)2(aq) + H2(g)
Reactions of carbonates with acids
Carbonates react with acid to produce a salt, carbon dioxide and water.
Copper (ii) carbonate + hydrochloric acid → copper (ii) chloride + carbon dioxide + water
CuCO3(s) + 2HCl(aq) → CuCl2(aq) + CO2(aq) + H2O(l)
Neutralisation reactions of acids with alkalis
Alkalis neutralise acids to produce a salt and water.
hydrochloric acid + sodium hydroxide → sodium chloride + water
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Neutralisation reactions of acids with insoluble bases
Bases neutralise acids to produce a salt and water.
sulphuric acid + copper(ii) oxide → copper(ii) sulphate + water
H2SO4(aq) + CuO(s) → CuSO4(aq) + H2O(l)
Ionisation of acids
Ionisation of weak acids
Weak acids are only partially ionised in water and produce less hydrogen ions.
ethanoic acid → hydrogen ions + ethanoate ions
CH3COOH(l) → H+(aq) + CH3COO−(aq)
Ionisation of strong acids
Strong acids fully ionise in water and produce more hydrogen ions than weak acids.
hydrochloric acid → hydrogen ions + chloride ions
HCl(aq) → H+(aq) + Cl−(aq)
Ionisation of alkalis
Ionisation of weak alkalis
Weak alkalis partially ionise in water to produce fewer hydroxide ions.
ammonia + water → ammonium ions + hydroxide ions
NH3(g) + H2O(l) → NH4(aq) + OH–(aq)
Ionisation of strong alkalis
Strong alkalis fully ionise in water to produce a lot of hydroxide ions.
sodium hydroxide → sodium ions + hydroxide ions
NaOH(s) → Na+(aq) + OH−(aq)
Displacement reactions
Displacement of metals
A reactive metal displaces a less reactive metal from a compound of its ions.
Magnesium + Copper (ii) nitrate → Magnesium nitrate + Copper
Mg(s) + Cu(NO3)2(aq) → Mg(NO3)2(aq) + Cu(s)
Electrolysis reactions
Electrolysis of molten lead (ii) bromide
Molten lead (ii) bromide can be electrolysed using carbon electrodes to produce lead at the cathode and bromine gas at the anode.
Cathode reaction:
Pb^^2+^^(l) + 2e– → Pb(l)
Anode reaction:
2Br–(l) – 2e– → Br2(g)
Overall reaction:
PbBr2(l) → Pb(l) + Br2(g)
Electrolysis of dilute sulphuric acid
Electrolysis of dilute sulphuric acid using inert electrodes produces hydrogen at the cathode and oxygen at the anode.
Anode reaction:
4OH−(aq) → 2H2O(l) + O2(g) + 4e–
Cathode reaction:
2H+(aq) + 2e– → H2(g)
Electrolysis of concentrated hydrochloric acid
Electrolysis of concentrated hydrochloric acid using inert electrodes produces hydrogen at the cathode and chlorine at the anode.
Cathode reaction:
2H+(aq) + 2e– → H2(g)
Anode reaction:
2Cl–(l) – 2e– → Cl2(g)
Electrolysis of aqueous copper (ii) sulphate using inert electrodes
Electrolysis of aqueous copper (ii) sulphate using inert electrodes produces copper at the cathode and oxygen at the anode.
Anode reaction:
4OH−(aq) → 2H2O(l) + O2(g) + 4e–
Cathode reaction:
Cu2+(aq) + 2e– → Cu(s)
Electrolysis of aqueous copper (ii) sulphate using copper electrodes
During electrolysis of aqueous copper (ii) sulphate using copper electrodes, the anode dissolves and copper is produced at the cathode.
Anode reaction:
Cu(s) → Cu2+(aq) + 2e–
Cathode reaction:
Cu2+(aq) + 2e– → Cu(s)
Decomposition reactions
Decomposition by catalyst
Hydrogen peroxide decomposes in the presence of a manganese (iv) oxide catalyst to produce water and oxygen.
hydrogen peroxide → water + oxygen
2H2O2(aq) → 2H2O(l) + O2(g)
Combustion reactions
Combustion of hydrocarbons
Hydrocarbons burn in plentiful supply of air to produce carbon dioxide and water. The reaction is exothermic.
methane + oxygen → carbon + water + energy dioxide
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
In limited oxygen supply, hydrocarbons burn to produce soot (unburnt carbon) and carbon monoxide. The reaction produces less heat energy.
methane + oxygen → carbon + carbon monoxide + water
2CH4(g) + 3O2(g) → 2CO(g) + 4H2O(l)