2.2 Group 2

Question 1

What happens to atomic radius down group 2?

Answer 1

Atomic radius increases down the group.

As one goes down the group, the atoms have more shells of electrons making the atom bigger

Question 2

What happens to melting points down group 2?

Answer 2

Melting points decrease down the group. The metallic bonding weakens as the atomic size increases. The distance between the positive ions and delocalized electrons increases. Therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken.

Question 3

What happens to first ionisation energy down group 2?

Answer 3

The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells.
In addition, the outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons

Question 4

What happens to reactivity down group 2?

Answer 4

Increases.

Question 5

What colour flame does Mg give and what is the equation?

Answer 5

The group 2 metals will burn in oxygen. Mg burns with a bright white flame. 2Mg + O2 —> 2MgO

Question 6

Describe the structure and melting point of MgO

Answer 6

MgO is a white solid with a high melting point due to its ionic bonding

Question 7

How does Mg react with steam?

Answer 7

Magnesium reacts in steam to produce magnesium oxide and hydrogen. The Mg would burn with a bright white flame.
Mg (s) + H2O (g)—>MgO (s) + H2 (g)

Question 8

How does Mg react with warm water?

Answer 8

Mg will also react with warm water, giving a different magnesium hydroxide product.
Mg + 2 H2O—>Mg(OH)2 + H2

Question 9

What happens to the vigour of group 2 metals down the group?

Answer 9

Increases

Question 10

What are the equations Ca, Sr and Ba react with cold water?

Answer 10

Ca + 2 H2O (l)—>Ca(OH)2 (aq) + H2 (g)
Sr + 2 H2O (l)—>Sr(OH)2 (aq) + H2 (g)
Ba + 2 H2O (l)—>Ba(OH)2 (aq) + H2 (g)

Question 11

What do you observe when group 2 reacts with cold water ?

Answer 11

• fizzing, (more vigorous down group)
• the metal dissolving, (faster down group)
• the solution heating up (more down group)
• with calcium a white precipitate appearing (less precipitate forms down group with other metals)

Question 12

Why is titanium useful?

Answer 12

Titanium is a very useful metal because it is abundant, has a low density and is corrosion resistant – it is used for making strong, light alloys for use in aircraft for example.

Question 13

How do you extract Titanium?

Answer 13

TiO2 (solid) is converted to TiCl4 (liquid) at 900C:
The TiCl4 is purified by fractional distillation in an argon atmosphere.
The Ti is extracted by Mg in an argon atmosphere at 500C

Question 14

Why is titanium expensive?

Answer 14

1. The expensive cost of the Mg
2. This is a batch process which makes it expensive because the process is slower (having to fill up and empty reactors takes time) and requires more labour and the energy is lost when the reactor is cooled down after stopping
3. The process is also expensive due to the argon, and the need to remove moisture (because TiCl4 is susceptible to hydrolysis).
4. High temperatures required in both steps

Question 15

Reactions to extract titanium?

Answer 15

TiO2 +2Cl2 +2C—>TiCl4 +2CO

TiCl4 + 2Mg—>Ti + 2 MgCl2

Question 16

What happens Group 2 solubility down the group?

Answer 16

Increases

Question 17

What is Calcium hydroxide used for?

Answer 17

It is used in agriculture to neutralise acidic soils.
An aqueous solution of calcium hydroxide is called lime water and can be used a test for carbon dioxide. The limewater turns cloudy as white calcium carbonate is produced.

Question 18

What happens to the solubility of group 2 sulphates down the group?

Answer 18

Decreases

Question 19

Sulphate ion test

Answer 19

BaCl2 solution acidified with hydrochloric acid is used as a reagent to
test for sulphate ions.
If acidified barium chloride is added to a solution that contains sulfate ions a
white precipitate of barium sulfate forms.