9.1 Group 2

Question 1

Describe the trend in atomic radius for group 2

Answer 1

Increases down the group because:
- More electron shells
- More shielding
- So bigger atoms

Question 2

Describe the trend in melting points for group 2

Answer 2

Decreases down the group because:
- Weaker metallic bond
- Metal ions get bigger so the delocalised electrons are further from the nucleus

Magnesium doesn’t follow the trend as it has a different lattice structure which is easier to melt

Question 3

Describe the trend in first ionisation energy for group 2

Answer 3

Decreases down the group because:
- Atoms get bigger so the electrons are further from the nucleus
- More shielding
- Therefore weaker attraction between electrons and nucleus

Question 4

What is the general equation for the reaction of group 2 elements and water?

Answer 4

M + 2H₂O → M(OH)₂ + H₂

Question 5

Describe the solubility of group 2 hydroxides

Answer 5

Increasing solubility down the group:

Mg(OH)₂ = Insoluble
Mg²⁺ + 2OH⁻ → Mg(OH)₂

Ca(OH)₂ = Slightly soluble
Ca²⁺ + 2OH⁻ → Ca(OH)₂

Sr(OH)₂ = Soluble

Ba(OH)₂ = Soluble

Question 6

Describe the solubility of group 2 sulphates

Answer 6

Decreasing solubility down the group:

MgSO₄ = Soluble

CaSO₄ = Slightly soluble
Ca²⁺ + SO₄²⁻ → CaSO₄

SrSO₄ = Insoluble
Sr²⁺ + SO₄²⁻ → SrSO₄

BaSO₄ = Insoluble
Ba²⁺ + SO₄²⁻ → BaSO₄

Question 7

Give the uses of magnesium hydroxide

Answer 7

Antacid as it will neutralise excess stomach acid

May also be used to neutralise acidic soils in agriculture

Question 8

Give the uses of barium sulphate

Answer 8

Barium meals - These are a form of medical tracer that allow internal tissues and organs to be imaged

Barium sulfate is toxic if it enters the bloodstream, however because it is insoluble, it cannot be absorbed into the blood

Question 9

Describe titanium extraction

Answer 9

Magnesium is used in the extraction of titanium from titanium chloride via a displacement reaction. Mg acts as a reducing agent.

TiCl4 + 2Mg -> 2MgCl2 + Ti

Question 10

Describe flue gas removal

Answer 10

Calcium oxide reacts with sulfur dioxide to remove it from factory pollutants and prevent it from being released into the atmosphere. This forms calcium sulfite and water.

CaO + 2H2O +SO2 -> CaSO3 + 2H2O