Reactions of Group 2 Elements (CIE AS Chemistry)

• 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