Reactions of Group 2 Elements (Cambridge (CIE) AS Chemistry)
Revision Note
Reactions of the Group 2 Elements
The Group 2 elements react with oxygen, water and dilute acids
Reaction of Group 2 elements table
Group 2 element | Reaction with oxygen | Reaction with water | Reaction with dilute HCl | Reaction with dilute H2SO4 |
|---|---|---|---|---|
Mg | Burns easily Bright white flame | Vigorous reaction with steam Very slow reaction with water | Reacts vigorously | Reacts vigorously |
Ca | Difficult to ignite Red flame | Reacts moderately Hydroxide formed | Reacts vigorously | Reaction is slowed by the formation of a sparingly soluble sulfate layer which coats the metal surface stopping hydrogen bubbles from rising |
Sr | Difficult to ignite Red flame | Reacts rapidly Hydroxide formed | Reacts vigorously | Reaction is quickly stopped by the formation of an insoluble sulfate layer on the metal surface |
Ba | Difficult to ignite Green flame | Reacts vigorously Hydroxide formed | Reacts vigorously | Reaction is quickly stopped by the formation of an insoluble sulfate layer on the metal surface |
Group 2 reactions with oxygen & water chemical equations
Group 2 element | Reaction with oxygen | Reaction with water |
|---|---|---|
Mg | 2Mg (s) + O2 (g) → 2MgO (s) | Mg (s) + H2O (l) → Mg(OH)2 (s) + H2 (g) * |
Ca | 2Ca (s) + O2 (g) → 2CaO (s) | Ca (s) + 2H2O (l) → Ca(OH)2 (s) + H2 (g) |
Sr | 2Sr (s) + O2 (g) → 2SrO (s) Sr (s) + O2 (g) → SrO2 (s) | Sr (s) + 2H2O (l) → Sr(OH)2 (aq) + H2 (g) |
Ba | 2Ba (s) + O2 (g) → 2BaO (s) Ba (s) + O2 (g) → BaO2 (s) | Ba (s) + 2H2O (l) → Ba(OH)2 (aq) + H2 (g) |
*Mg reacts with steam: Mg (s) + 2H2O (g) → MgO (s) + H2 (g)
Group 2 reactions with dilute hydrochloric acid & dilute sulfuric acid chemical equations
Group 2 element | Reaction with dilute HCl | Reaction with dilute H2SO4 |
|---|---|---|
Mg | Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) | Mg (s) + H2SO4 (aq) → MgSO4 (aq) + H2 (g) |
Ca | Ca (s) + 2HCl (aq) → CaCl2 (aq) + H2 (g) | Ca (s) + H2SO4 (aq) → CaSO4 (s) + H2 (g) |
Sr | Sr (s) + 2HCl (aq) → SrCl2 (aq) + H2 (g) | Sr (s) + H2SO4 (aq) → SrSO4 (s) + H2 (g) |
Ba | Ba (s) + 2HCl (aq) → BaCl2 (aq) + H2 (g) | Ba (s) + H2SO4 (aq) → BaSO4 (s) + H2 (g) |
The reaction of all metals with oxygen follows the following general equation:
2M (s) + O2 (g) → 2MO (s)
Where M is any metal in Group 2
Remember that Sr and Ba also form MO2
The reaction of all metals with water follows the following general equation:
M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)
The exceptions to this general equation are:
Be which does not react with water
Mg which forms MgO (s) and H2 (g)
The reaction of all metals with dilute HCl follows the following general equation:
M (s) + 2HCl (aq) → MCl2 (aq) + H2 (g)
The reaction of all metals with dilute H2SO4 follows the following general equation:
M (s) + H2SO4 (aq) → MSO4 (aq) + H2 (g)
Remember that CaSO4, SrSO4 and BaSO4 are insoluble
Examiner Tips and Tricks
Learn the general equation for the reaction with oxygen, water and dilute HCl / H2SO4 and the exceptions instead of memorizing the entire table!
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