3.2.2 Group 2, the alkaline earth metals

Question 1

What is the trend in first ionisation energy of group 2?

Answer 1

It decreases down the group

This is because the electron is further from the nucleus so there is less attraction and increased shielding

Question 2

What is the trend in boiling point of group 2?

Answer 2

It decreases down the group
The distance between the delocalised sea of electrons and the nucleus increases
This decreases the strength of the metallic bond as electrostatic attraction is weaker

Question 3

Which group 2 element does not follow the trend in boiling points?

Answer 3

Magnesium

Question 4

What is the trend in atomic radius of group 2 elements?

Answer 4

It increases as you go down the group

Atoms get bigger because each element has another shell full of elements

Question 5

What is the equation for the reaction between beryllium and water? What are the conditions?

Answer 5

Be + H2O = BeO + H2

High temperatures

Question 6

What is the equation for the reaction between magnesium and water? What are the conditions?

Answer 6

Mg + H2O = MgO + H2

Reacts rapidy with steam

Question 7

What is the trend in reactivity of group 2 elements with water?

Answer 7

Increase in reactivity

Can react with cold water, to form hydrogen gas and hydroxide: redox reactions

Question 8

What is a non-medical use of barium chloride?

Answer 8

It’s solubility is also useful when testing for sulfate ions in a solution
It allows a precipitate of barium sulfate to form indicating the completion of the reaction

Question 9

Why is magnesium hydroxide suitable for ingestion as a digestive medication?

Answer 9

It is a weak base so is non-toxic which allows it to be consumed in small quantities

Question 10

How does magnesium hydroxide and calcium hydroxide compare in terms of strength? What use does this make calcium hydroxide suitable for?

Answer 10

Calcium hydroxide is a stronger base

Agriculture to adjust the pH of acidic soil and lakes

Question 11

What is rutile?

Answer 11

Titanium ore

Question 12

What is the equation for the reaction between titanium ore and chlorine? Why does the product of this reaction have to undergo fractional distillation?

Answer 12

TiO2 + 2Cl2 + 2C = TiCl4 + 2CO
To seperate titanium chloride from the other chlorides
A range of metal chlorides are formed because there are other metal chlorides in the ore

Question 13

What are the reaction conditions for the reaction between titanium (IV) chloride and magnesium?

Answer 13

Molten magnesium

Titanium (IV) chloride vapour

Question 14

Why is dilute hydrochloric acid added after the reaction between titanium (IV) chloride and magnesium?

Answer 14

To react with excess magnesium to form magnesium chloride

Question 15

Why can’t carbon be used in the reaction between titanium (IV) chloride and magnesium?
What is another reducing agent that can be used?

Answer 15

Titanium will form a carbide so you can’t get pure metal

Sodium

Question 16

Why is titanium carbide not useful?

Answer 16

It is very brittle so not useful

Question 17

Why is titanium extraction expensive?

Answer 17

Magnesium/sodium also have to be extracted from their ores before they can be used in the reaction

Question 18

Why is group 2 called the alkaline earth metals?

Answer 18

Because their oxides and hydroxides are alkaline

Question 19

What is the electronic configuration of group 2?

Answer 19

[Noble gas] s

Question 20

What is the bonding present in the Alkaline Earth metals?

Answer 20

Metals with high melting points
Giant metallic structure
Going down the group, the delocalised sea of electrons is further away from the nucleus
Therefore the metallic structure is weaker going down the bond
Therefore the melting point decreases down the group
Magnesium doesn’t follow this trend and has the lowest melting point

Question 21

What are the rules for ionisation energy for group 2 elements?

Answer 21

They lose their two outer electrons to form +2 ions
The amount of energy is equal to the sum of the first and second ionisation energies
First and second ionisation energy decreases down the group as the distance and inner shielding increases

Question 22

What is the rule of reactivity of group 2 elements?

Answer 22

The metals get more reactive going down the group

Question 23

What is the trend in reactivity for the group 2 element’s reaction with water?

Answer 23

Reactivity increases down the group
Magnesium reacts very slowly with cold water
Calcium reacts vigorously even with cold water

Question 24

What is a use of Mg(OH)2?

Answer 24

Milk of magnesia

Used in indigestion to neutralise excess stomach acids

Question 25

What is a use of Calcium hydroxide?

Answer 25

Used to treat acidic soil to be closer to the optimum

Question 26

What is the trend in solubilities of hydroxides?

Answer 26

More soluble going down the group

Hydroxides are all white solids

Question 27

How soluble is magnesium hydroxide?

Answer 27

Magnesium hydroxide is almost insoluble

Question 28

How soluble is calcium hydroxide?

Answer 28

Calcium hydroxide is sparingly soluble

Question 29

How soluble is strontium hydroxide?

Answer 29

Strontium hydroxide is more soluble than calcium hydroxide

Question 30

How soluble is barium hydroxide?

Answer 30

Barium hydroxide completely dissolves to produce a strongly alkaline solution
Ba(OH)2 = Ba2+ + 2OH-

Question 31

What is the trend in solubility of group 2 sulfates?

Answer 31

They become less soluble down the group

Question 32

How soluble is barium sulfate?

Answer 32

Virtually insoluble

Question 33

What is a use of barium sulfate?

Answer 33

Can be taken by mouth as a barium meal to outline the gut in medical x-rays
Barium is toxic but barium sulfate is safe because it is insoluble

Question 34

How can barium chloride be used to test for sulfate ions in solution?

Answer 34

Solution is first acidified with nitric or hydrochloric acid to remove carbonate ions
Then barium chloride is added
If a sulfate is present, an insoluble precipitate of white barium sulfate is produced

Question 35

What is the general reaction between group 2 elements and water?

Answer 35

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

Question 36

What is formed when a group 2 chloride is added to sodium hydroxide?

Answer 36

Group 2 hydroxides

Question 37

What is formed when a group 2 chloride is added to sulfuric acid?

Answer 37

Group 2 sulfates