A level Chemistry - Group 2 reactions and uses

Mg + water (l) reaction

Mg + 2H₂O (l) → Mg(OH)₂ + H₂

Mg + water (g) reaction

Mg + H₂O (g) → MgO + H₂

Mg + steam observations

• Bright white light

• White solid forms

Ca + water reaction

Ca + 2H₂O (l) → Ca(OH)₂ + H₂

Solubility of hydroxides down Group 2

increases

Solubility of sulfates down Group 2

decreases

Use of Mg

Extraction of titanium

Use of Mg(OH)₂

Antacid

Use of Ca(OH)₂

Neutralises acidic soil

Use of CaO/CaCO₃

Removes SO₂ from flue gases

Use of BaSO₄

Absorbs X rays

Why is BaSO₄ used for X-rays?

It is insoluble so is not absorbed into the blood

Extraction of titanium equation

TiCl₄ + 2Mg → Ti + 2MgCl₂

Use of BaCl₂

Acidified and used to test for sulfate ions

Why is BaCl₂ acidified before testing for sulfate ions?

To remove CO₃^2- as some CO₂ may dissolve in the solution

Trend in first ionisation energy down Group 2

decreases

Why does first ionisation energy decrease down the group?

1. Number of electrons and number of cells increases down the group

2. Shielding increases

3. Nuclear charge also increases but effective nuclear charge decreases

4. Attraction between nucleus and other electrons decreases

5. Less energy is required to remove outer electron

Trend in melting points down Group 2

decreases

Why does melting point decrease down Group 2?

• Size of metal ion increase

• Attraction between positive metal ions and sea of delocalised electrons decreases