Flashcards · 9701 · AS Topic 10

Group 2 (AS Level) flashcards

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Why does reactivity increase down Group 2?: Atomic radius and shielding increase, so the two outer electrons are lost more easily, despite the greater nuclear charge.
Magnesium with cold water and with steam: Cold water: very slow, gives Mg(OH)₂ + H₂. Steam: vigorous, gives MgO + H₂ (Mg + H₂O → MgO + H₂).
Solubility trends of the Group 2 hydroxides and sulfates: Hydroxides: solubility increases down the group (Mg(OH)₂ sparingly soluble → Ba(OH)₂ soluble). Sulfates: solubility decreases (MgSO₄ soluble → BaSO₄ insoluble).
Thermal decomposition of Group 2 carbonates and nitrates, and the trend: MCO₃ → MO + CO₂ 2M(NO₃)₂ → 2MO + 4NO₂ + O₂ (brown NO₂) Thermal stability increases down the group.
Why does the reaction of barium with dilute sulfuric acid stop almost at once?: Insoluble BaSO₄ coats the metal and blocks further contact with the acid. It is a solubility effect, not low reactivity.
Uses of Ca(OH)₂, CaCO₃, MgO and BaSO₄: Ca(OH)₂: neutralises acidic soils. CaCO₃: removes SO₂ from flue gases; cement and iron making. MgO: refractory furnace lining. BaSO₄: barium meal (insoluble, so safe).
Group 2 oxides, hydroxides and carbonates with dilute hydrochloric acid: MO + 2HCl → MCl₂ + H₂O M(OH)₂ + 2HCl → MCl₂ + 2H₂O MCO₃ + 2HCl → MCl₂ + H₂O + CO₂