CIE AS Chemistry (9701) exams from 2022

Revision Notes

2.2.2 Reactions of Group 2 Oxides, Hydroxides & Carbonates

Reactions of Group 2 Oxides, Hydroxides & Carbonates

Reactions of group 2 oxides

  • 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 oxide reactions with water table

Group 2 - Table 1_Reactions of Group 2 Oxides, Hydroxides & Carbonates, downloadable AS & A Level Chemistry revision notes

  • Remeber that:

oxide + water → hydroxide

and that calcium hydroxide is also called limewater

  • The Group 2 metal oxides are white solids which form colourless solutions of metal chlorides when they react with a dilute acid
  • The reaction of a metal oxide with a dilute acid is a neutralisation reaction

Group 2 oxide reactions with dilute acids table

Group 2 - Table 3_Reactions of Group 2 Elements, downloadable AS & A Level Chemistry revision notes

  • Going down the group, the Group 2 sulfates become less and less soluble
  • These insoluble sulfates form at the surface of the oxides which means that the solid oxide beneath it can’t react with the acid
  • This can be prevented by using the oxide in powder form and stirring in which case signification neutralisation can take place
  • Remember that:

oxide + dilute hydrochloric acid → salt + water

oxide + dilute sulfuric acid → sulfate + water

Reactions of group 2 hydroxides

  • The Group 2 metal hydroxides form colourless solutions of metal chlorides 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 table

Group 2 - Table 3_Reactions of Group 2 Oxides, Hydroxides & Carbonates, downloadable AS & A Level Chemistry revision notes

  • Remember that:

hydroxide + dilute acid → salt + water

hydroxide + dilute sulfuric acid → sulfate + water

Reactions of group 2 carbonates

  • All Group 2 carbonates (except for BeCO3) are insoluble in water
  • All Group 2 carbonates will form soluble chloride salts, water and carbon dioxide gas when reacted with dilute hydrochloric acid
  • The carbonates of Ca, Sr and Ba form as an insoluble sulfate layer on their solid carbonates which stops any further reaction after the initial bubbling (effervescence) of carbon dioxide gas is seen

Group 2 carbonate reactions with dilute acids

Group 2 - Table 4_Reactions of Group 2 Oxides, Hydroxides & Carbonates, downloadable AS & A Level Chemistry revision notes

  • Remember that:

carbonate + dilute hydrochloric acid → salt + water + carbon dioxide

carbonate + dilute sulfuric acid → sulfate + water + carbon dioxide

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