Group 2 metals-inorganic chemistry Flashcards
How do Group 2 metals react with water?
General equation:
M+2𝐻2O→M(OH)2+𝐻2
Mg reacts very slowly with cold water but faster with steam.
Ca, Sr, Ba react increasingly vigorously down the group, forming hydroxides and hydrogen gas.
✅ Reactivity increases down the group.
How is magnesium used to extract titanium?
Titanium (IV) chloride (TiCl₄) is reduced by Mg in an inert atmosphere:
TiCl4+2𝑀𝑔→Ti+2𝑀𝑔𝐶𝑙
Magnesium acts as a reducing agent.
This prevents oxygen contamination, which would make titanium brittle.
How does solubility of Group 2 hydroxides change down the group?
Increases down the group.
More dissociation into OH⁻ ions → more alkaline solution.
Mg(OH)₂ is sparingly soluble, but Ba(OH)₂ is highly soluble.
What are the uses of Mg(OH)₂ and Ca(OH)₂?
Mg(OH)₂ (Milk of Magnesia): Used as an antacid to neutralise stomach acid.
Mg(OH)2+2𝐻𝐶𝑙→MgCl2+2𝐻2𝑂
Ca(OH)₂ (Slaked Lime): Used in agriculture to neutralise acidic soil.
✅ Both act as bases and neutralise acids.
How is SO₂ removed from flue gases?
CaO or CaCO₃ reacts with SO₂ to form calcium sulfite (CaSO₃), which prevents acid rain.
Equations:
CaO + SO2-> CaSO3
CaCO3 + SO2 -> CaSO3 + CO2
This process is called flue gas desulfurisation.
How does solubility of Group 2 sulfates change down the group?
Decreases down the group.
BaSO₄ is completely insoluble in water.
MgSO₄ is soluble, but BaSO₄ is insoluble.
Why is BaSO₄ used in medicine?
Barium sulfate (BaSO₄) is used as a contrast agent in X-rays.
It is insoluble and non-toxic (even though barium ions are toxic).
✅ Barium meals help doctors see digestive organs in X-ray scans.
How does BaCl₂ test for sulfate ions?
Ba²⁺ reacts with SO₄²⁻ to form BaSO₄, a white precipitate:
Ba2+SO42−→BaSO4(𝑠)
BaSO₄ is insoluble → confirms presence of sulfate ions.
✅ HCl or HNO₃ is added to remove CO₃²⁻ ions, which could give a false positive result.
