Reactions of Group 2 (Oxford AQA International A Level Chemistry)
Revision Note
Written by: Philippa Platt
Reviewed by: Stewart Hird
Reactions of Group 2
The reactivity of the Group 2 elements increases as you go down the group
This trend is shown by the reactivity with water:
M (s) + 2H2O (l) → M(OH)2 (aq) + H2 (g)
The reaction is also a redox reaction
M increases oxidation state from 0 to +2 so is oxidised
Hydrogen decreases in oxidation state from +1 to 0 so is reduced
Group 2 reactions with water
Group 2 element | Reaction with water |
|---|---|
Mg | Mg (s) + 2H2O (l) → Mg(OH)2 (s) + H2 (g) * |
Ca | Ca (s) + 2H2O (l) → Ca(OH)2 (s) + H2 (g) |
Sr | Sr (s) + 2H2O (l) → Sr(OH)2 (aq) + H2 (g) |
Ba | Ba (s) + 2H2O (l) → Ba(OH)2 (aq) + H2 (g) |
*Mg reacts with steam: Mg (s) + H2O (g) → MgO (s) + H2 (g)
Examiner Tips and Tricks
The reaction of magnesium with water is very slow compared to the vigorous reaction of magnesium with steam to form MgO and H2
Make sure you check information given in the question if asked about the reactions of magnesium
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