3.2.2 Group 2 The alkaline earth metals

Question 1

What is the trend in atomic radius in group 2 (Mg-Ba) and why?

Answer 1

It generally increases as you go down the group as every element has more electron shells, therefore although there is an increase in nuclear charge the effect of Shielding and Distance outweighs it.

Question 2

What is the trend in First Ionisation energy in group 2 (Mg-Ba) and why?

Answer 2

It decreases down the group, this is because as you go down the group the shielding and distance from nucleus to electrons increases

Question 3

What is the trend in Melting point energy in group 2 (Mg-Ba) and why?

Answer 3

Generally decreases as when atomic size increases the metallic bonding decreases as delocalised electrons are further from nucleus,
An exception to this is Mg as it is in a different crystal structure then the rest of elements in this group

Question 4

What is the trend in Reactivity energy in group 2 (Mg-Ba) and why?

Answer 4

Reactivity increases as you down the group as first ionisation energy decreases as you go down the group making it easier t make a 2+ metal ion

Question 5

What happens when Mg reacts with water (speed of reaction and observation)?

Answer 5

Speed of reaction: Very slow
Observation:
Mg Very slow / almost none Few bubbles, forms Mg(OH)₂ slowly

Question 6

What happens when Ca reacts with water (speed of reaction and observation)?

Answer 6

Speed of reaction: Reacts Readily
Observation: Effervescence and white precipitate

Question 7

What happens when Sr reacts with water (speed of reaction and observation)?

Answer 7

Speed of reaction: Reacts quickly
Observation: More effervescence

Question 8

What happens when Ba reacts with water (speed of reaction and observation)?

Answer 8

Speed of reaction: Reacts very rapidly
Observation: Vigorous Bubbling, solution becomes alkaline

Question 9

Trend of solubility of group 2 hydroxides?

Answer 9

Group 2 hydroxides increase in solubility as you go down the group

Question 10

How is Magnesium used in the extraction of Titanium?

Answer 10

Titanium ore is reacted with chlorine and carbon to form TiCl4 (gas), which is purified through distillation and then it is reduced by Magnesium at high temperature (1000 C)

Question 11

Why is magnesium used for the extraction of titanium?

Answer 11

Because Magnesium is a good reducing agent (allowing it to displace Titanium from TiCl4)

It is cheap, abundant

Question 12

Use of Magnesium Hydroxide (Mg(OH)2)

Answer 12

• Magnesium hydroxide is used to in indigestion tablets (heartburn tablets) to neutralise excess stomach acid

Question 13

Use of Calcium Hydroxide (Ca(OH)2)

Answer 13

Calcium hydroxide is used in agriculture to neutralise acid soils

Question 14

Use of calcium oxide (CaO) and calcium carbonate(CaCO3)?

Answer 14

They are mixed with water to make a slurry (alkali+water) and sprayed in industrial tubes to remove sulfur dioxide (SO2)

Question 15

Trend in solubility of group 2 sulfates

Answer 15

The solubility decreases as you go down the group with BaSO4 being insoluble

Question 16

What is the test for sulfate ions?

Answer 16

• Firstly add HCL to a solution containing
  sulfate ions
  remove impurities (sulfites and carbonates)
• Secondly add acidified Barium chloride (BaCl2) to solution
• White precipitate forms displaying the presence of sulfate ions

Question 17

Medical Use of Barium Sulfate BaSO4 and why is it used?

Answer 17

A Barium meal is taken by a patient and as the barium sulfate coats the tissues they can be seen in an x-ray
x-rays pass straight through soft tissue therefore cannot be seen in an x-ray but Barium sulfate is opaque to x-rays therefore displaying in an x-ray.

BaSO4 is used due to its insolubility