2.2 Group 2 Flashcards
What is the trend in atomic radius down Group 2?
Atomic radius increases down the group because atoms have more shells of electrons, making them bigger.
What is the trend in 1st ionisation energy down Group 2?
It decreases because the outermost electrons are further from the nucleus and more shielded by inner electrons, reducing nuclear attraction.
What is the trend in melting points down Group 2?
Melting points decrease down the group due to weaker metallic bonding as atomic size increases and electrostatic attraction weakens.
How does the reactivity of Group 2 metals change down the group?
Reactivity increases down the group.
What is the balanced equation for magnesium reacting with oxygen?
2 Mg + O₂ → 2 MgO
Why must magnesium ribbon be cleaned before reacting it with acid?
It may have a layer of MgO that reacts differently, giving false results when testing reaction rates.
How does magnesium react with steam?
Mg(s) + H₂O(g) → MgO(s) + H₂(g); burns with bright white flame, white powder forms.
How do Group 2 metals react with cold water (example with calcium)?
Ca + 2 H₂O(l) → Ca(OH)₂(aq) + H₂(g)
What observations are made when Group 2 metals react with water?
Fizzing, metal dissolving, heat release, and a white precipitate with Ca (less precipitate down the group).
What is the reaction for Mg with warm water?
Mg + 2 H₂O → Mg(OH)₂ + H₂; slower than steam reaction and no flame.
Why can’t titanium be extracted using carbon or electrolysis?
Carbon forms titanium carbide (TiC); electrolysis requires very pure Ti. Instead, Mg is used to reduce TiCl₄.
What are the key steps in extracting titanium with magnesium?
- TiO₂ + 2Cl₂ + 2C → TiCl₄ + 2CO
- TiCl₄ purified by fractional distillation
- TiCl₄ + 2Mg → Ti + 2MgCl₂
Why is titanium expensive despite being abundant?
High Mg cost, batch process, use of argon, moisture removal, and high temperatures required.
How does calcium oxide remove sulfur dioxide in flue gas desulfurisation?
A14: SO₂ + CaO → CaSO₃; forms calcium sulfite, used to make plasterboard.
How does BaCl₂ test for sulfate ions?
Forms a white precipitate of BaSO₄.
Equation: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
Why is BaSO₄ used as a ‘barium meal’ in medicine?
It absorbs X-rays and is safe due to very low solubility, preventing absorption into the bloodstream.
What is the solubility trend of Group 2 sulfates?
Solubility decreases down the group; BaSO₄ is the least soluble.
What is the solubility trend of Group 2 hydroxides?
Solubility increases down the group.
How is calcium hydroxide used agriculturally?
To neutralize acidic soil.
What happens when limewater (Ca(OH)₂ solution) is exposed to CO₂?
Turns cloudy due to formation of white CaCO₃ precipitate.
Equation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
What is magnesium hydroxide used for?
As milk of magnesia to neutralize stomach acid and relieve constipation.
How are insoluble salts like BaSO₄ made?
By mixing appropriate ionic solutions — a precipitation reaction.
What is an example of a precipitation reaction forming BaSO₄?
Full equation: Ba(NO₃)₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2 NaNO₃(aq)
Ionic: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
What are spectator ions?
Ions that don’t change state or oxidation number during a reaction and are not included in ionic equations.
What are two filtration methods used in labs?
• Gravitational filtration: for small solids, uses standard funnel.
• Vacuum filtration: for large solids, uses Büchner flask and funnel with water pump.
