Group 2- Alkali Earth Metals

Question 1

List the elements group 2

Answer 1

Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba)

Question 2

State and explain the trends in atomic radius

Answer 2

Atomic radius increases. This is because the main energy levels increase (more electrons)

Question 3

State and explain the trends in ionisation energy

Answer 3

1st IE decreases. This is because the ions get bigger so there is a weaker attraction between the outer electron and nucleus

Question 4

State and explain the trends in melting and boiling points

Answer 4

Melting point decreases. Ionic radius increases, attraction between delocalised electrons and metal cation weakens, metallic bonds get longer and weaker and easier to break.

Question 5

General equation for reaction of group 2 metal with water

Answer 5

M (s) + 2H₂O(l) ——–> M(OH)₂ (aq) + H₂(g)

Question 6

Solubilities of Mg-Ba sulphates

Answer 6

Mg- Very soluble
Ca- Soluble
Sr- Sparingly soluble
Ba- Insoluble

Question 7

Solubilites of Mg-Ba hydroxides

Answer 7

Mg- Sparingly soluble
Ca- Soluble
Sr- Soluble
Ba- Soluble

Question 8

What is barium sulphate used for in medicine?

Answer 8

Barium meal- ingested by patient for visibility on x-rays, not harmful because it is insoluble

Question 9

What is magnesium hydroxides for in medicine?

Answer 9

‘Milk of Magnesia’, used to neutralise stomach acid

Question 10

Why is calcium hydroxide/oxide used in agriculture?

Answer 10

‘Slaked lime’ neutralisation of soil

Question 11

How is barium chloride used to test for sulphate ions?

Answer 11

• Add nitric acid to remove carbonate and hydroxide ions
• Add BaCl₂ to the substance
• White precipitate= sulphate ions
• Ba²⁺ + SO₄²⁻———-> BaSO₄

Question 12

How is CaO used to remove SO₂ from flue gases? (with equations)

Answer 12

• CaO mixed with water- alkaline suspension
• Mixed with air and sprayed, reacts with SO₂ to create solid CaSO₄
  CaCO₃ + SO₂ ———–> CaSO₃ +CO₂
  CaO + SO₂ ———-> CaSO₃

Question 13

What are flue gases?

Answer 13

(Acidic) gases like SO₂ produced by power stations that are harmful to the environment (i.e. acid rain)

Question 14

Use of Mg in the extraction of Ti from TiCl₄

Answer 14

• TiO₂ + 2Cl₂ + C ———–> TiCl₄ + CO₂
• TiCl₄ + 2Mg ———–> 2MgCl₂ + Ti
  Conditions: Molten Mg, Argon atmosphere
  Benefits of Ti: forms layer of TiO₂, prevents reactions with bodily fluids- non-corrosive

Question 15

Why can’t Carbon be used for Ti extraction

Answer 15

Titanium carbide formed is brittle