Reactions with water and oxygen

• The reaction of group 2 metals with oxygen follows the following general equation:

2M (s) + O2?(g) → 2MO (s)

Where M is any metal in group 2

Remember than Sr and Ba?also?form a peroxide, MO2

• The reaction of all metals with water follows the following general equation:

M (s) + 2H2O (l) → M(OH)2?(s) + H2?(g)

Except for, Be which does not react with water

Group 2 Metals reacting with Water and with Oxygen - Equations

• Magnesium reacts?extremely slowly?with cold water:

Mg (s) + 2H2O (l) → Mg(OH)2?(aq) + H2?(g)

• The solution formed is?weakly?alkaline?(pH 9-10) as?magnesium hydroxide?is only?slightly soluble
• However, when magnesium is?heated?in steam, it reacts?vigorously?with steam to make magnesium oxide and hydrogen gas:

Mg (s) + H2O (g) → MgO (s) + H2?(g)

Reactions with chlorine

• Group 2 metals react with chlorine gas to give the metal chloride
  • For example

Mg (s) + Cl2?(g) → MgCl2?(s)

Reactions of Group 2 oxides with water

• All Group 2 oxides are?basic, except for BeO which is?amphoteric?(it can act both as an acid and base)
• Group 2 oxides react water to form?alkaline?solutions which get more?alkaline?going down the group

Group 2 Oxides reacting with Water

• Remember that:

oxide + water → hydroxide

• You should know that calcium hydroxide, when in solution, is also called?limewater

Reactions of Group 2 oxides with acid

• Group 2 sulfates also form when a Group 2 oxide is reacted with sulfuric acid
• The?insoluble sulfates?form at the?surface?of the oxide, which means that the solid oxide beneath it can’t react with the acid
• This can be prevented to an extent by using the oxide in?powder?form and?stirring, in which case neutralisation can take place
• Remember that:

oxide + dilute hydrochloric acid → chloride + water

oxide + dilute sulfuric acid → sulfate + water

Reactions of Group 2 hydroxides

• The Group 2 metal hydroxides form?colourless solutions of metal salts?when they react with a dilute acid
• The sulfates decrease in?solubility?going down the group (barium sulfate is an insoluble white precipitate)

Group 2 Hydroxide Reactions with Dilute Acids

• Remember that:

hydroxide + dilute hydrochloric acid → chloride + water

hydroxide + dilute sulfuric acid → sulfate + water