3.2.2 Group 2, The Alkaline Earth Metals
The Use of Magnesium to Extract
First Ionisation Energy Melting Point
Titanium
- Decreases - Decreases
TiO₂ + 2C + 2Cl₂ → TiCl₄ + 2CO
- Atomic radius increases - Positive ion gets larger
TiCl₄ + 2Mg → 2MgCl₂ + Ti
- More shielding therefore less attraction - So less attraction for delocalised electrons
- So weaker metallic bonding
Reactivity Explain Why Water Should Not be Used to Put Out a
Atomic Radius Fire in Mhich Magnesium Metal is Burning (2)
- Increases
- Increases - Hydrogen produced
- More shielding
- More shells of electrons - Hydrogen is highly flammable
- Outer electron are further from nucleus
- Less nuclear attraction between nucleus and
outer electron and so it is easily lost
Explain Why BaCl₂ is Acidified When Testing For
Sulfate Ions (2)
Reactions with Water:
HCl reacts with carbonate impurities found in salts which
Mg (s) + 2H₂O (l) → Mg(OH)₂ (aq) + H₂ (g) Observations with Calcium (pH 14):
would form a white barium carbonate precipitate giving a
Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g) - White precipitate forms
false result
Sr (s) + 2H₂O (l) → Sr(OH)₂ (aq) + H₂ (g) - Effervescence (fizzing)
Ba (s) + 2H₂O (l) → Ba(OH)₂ (aq) + H₂ (g) - Solution Heats Up
Magnesium can also React with Steam: Mg(OH)₂ is sparingly soluble so it cannot be used
Mg (s) + H₂O (g) → MgO (s) + H₂ (g) in the titration of weak acids for example
- Magnesium has a bright white flame
- White solid is produced State Why Sulfuric Acid Should Not be Used to
Acidify Barium Chloride
- Sulfuric acid contains sulfate ions
- This would form a (white) precipitate Solubility of
hydroxides
increase
Mg(OH)₂ MgSO₄
Ca(OH)₂ CaSO₄
Uses of Group 2 Metals Solubility of
Mg(OH)₂: Used as an antacid for the relief of indigestion as it neutralises excess acid in the stomach Sr(OH)₂ SrSO₄ sulfates decrease
Ca(OH)₂: Used to reduce soil acidity and provide calcium ions which are essential for plant growth
BaSO₄ (insoluble): Barium meal to outline guts for an X-ray (it is safe because it is insoluble) Ba(OH)₂ BaSO₄
BaCl₂: To test for sulphate ions (white precipitate produced)
The Use of Magnesium to Extract
First Ionisation Energy Melting Point
Titanium
- Decreases - Decreases
TiO₂ + 2C + 2Cl₂ → TiCl₄ + 2CO
- Atomic radius increases - Positive ion gets larger
TiCl₄ + 2Mg → 2MgCl₂ + Ti
- More shielding therefore less attraction - So less attraction for delocalised electrons
- So weaker metallic bonding
Reactivity Explain Why Water Should Not be Used to Put Out a
Atomic Radius Fire in Mhich Magnesium Metal is Burning (2)
- Increases
- Increases - Hydrogen produced
- More shielding
- More shells of electrons - Hydrogen is highly flammable
- Outer electron are further from nucleus
- Less nuclear attraction between nucleus and
outer electron and so it is easily lost
Explain Why BaCl₂ is Acidified When Testing For
Sulfate Ions (2)
Reactions with Water:
HCl reacts with carbonate impurities found in salts which
Mg (s) + 2H₂O (l) → Mg(OH)₂ (aq) + H₂ (g) Observations with Calcium (pH 14):
would form a white barium carbonate precipitate giving a
Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g) - White precipitate forms
false result
Sr (s) + 2H₂O (l) → Sr(OH)₂ (aq) + H₂ (g) - Effervescence (fizzing)
Ba (s) + 2H₂O (l) → Ba(OH)₂ (aq) + H₂ (g) - Solution Heats Up
Magnesium can also React with Steam: Mg(OH)₂ is sparingly soluble so it cannot be used
Mg (s) + H₂O (g) → MgO (s) + H₂ (g) in the titration of weak acids for example
- Magnesium has a bright white flame
- White solid is produced State Why Sulfuric Acid Should Not be Used to
Acidify Barium Chloride
- Sulfuric acid contains sulfate ions
- This would form a (white) precipitate Solubility of
hydroxides
increase
Mg(OH)₂ MgSO₄
Ca(OH)₂ CaSO₄
Uses of Group 2 Metals Solubility of
Mg(OH)₂: Used as an antacid for the relief of indigestion as it neutralises excess acid in the stomach Sr(OH)₂ SrSO₄ sulfates decrease
Ca(OH)₂: Used to reduce soil acidity and provide calcium ions which are essential for plant growth
BaSO₄ (insoluble): Barium meal to outline guts for an X-ray (it is safe because it is insoluble) Ba(OH)₂ BaSO₄
BaCl₂: To test for sulphate ions (white precipitate produced)
