3.2.2 Group 2, Alkaline Earth Metals

Question 1

What is the trend in atomic radius in group 2? (2)

Answer 1

Down the group, it increases

This is because there are extra electron shells being added

Question 2

What is the trend in first ionisation energy in group 2? (4)

Answer 2

Decreases down the group
Shielding increases as there are extra inner shells
Atomic radius increases so electron is further away from nucleus
Nuclear charge increasing is overridden by the effect of extra shells

Question 3

What is the trend in melting point in group 2? (5)

Answer 3

Generally decreases down group
Metal ions get bigger
Number of delocalised electrons and charge on ions stays the same
Delocalised electrons are further away from positive nuclei
Anomaly at Mg - much lower as crystal structure changes

Question 4

What is the trend in reactivity in group 2? (2)

Answer 4

Increases down group

This is because first ionisation energy decreases

Question 5

How do group 2 metals react with water?

Answer 5

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

Question 6

How does magnesium react with steam?

Answer 6

Mg (s) + H2O (g) > MgO (aq) + H2 (g)

Question 7

How does the solubility of the metal hydroxides change down group 2? (2)

Answer 7

Increases

Mg(OH)2 is sparingly soluble

Question 8

How does the solubility of the metal sulphates change down group 2? (2)

Answer 8

Decreases

BaSO4 is insoluble

Question 9

What is magnesium hydroxide used for?

Answer 9

In indigestion tablets as an antacid

Question 10

What is calcium hydroxide used for?

Answer 10

Neutralising acidic soil

Question 11

How is titanium extracted? (3)

Answer 11

Titanium oxide, TiO2, is heated with carbon in a stream of chlorine gas to form TiCl4
Titanium chloride is purified by fractional distillation before being reduced by magnesium in a furnace (1000°c)
TiCl4 (g) + 2Mg (l) > Ti (s) + 2MgCl (l)

Question 12

How is sulphur dioxide removed from flue gases? (3)

Answer 12

Wet scrubbing - removed with an alkali such as a slurry lime (CaO) or limestone (CaCO3) mixed with water
CaO (s) + 2H2O (l) + SO2 (g) > CaSO3 (s) + 2H2O (l)
CaCO3 (s) + 2H2O (l) + SO2 (g) > CaSO3 (s) + 2H2O (l) + CO2 (g)

Question 13

How are sulphate ions tested for? (2)

Answer 13

Add acidified (HCl) barium chloride (acid gets rid of sulphites or carbonates that would produce a positive result)
A white precipitate of barium sulphate will form if present

Question 14

What is barium sulphate used for? (2)

Answer 14

Barium meals - coats soft tissues so they show up on X-rays

Safe because barium sulphate is insoluble so forms a suspension not a solution