Topic 14- Group 2- The Alkaline Earth metals

Question 1

Trends of group 2 metals.

Answer 1

Atomic radius increases as you go down the group
First ionisation energy decreases down the group
Melting point decreases as you go down a group

Question 2

Trend in reaction with water down group 2 and general equation for reaction with water and steam.

Answer 2

Rate of reaction with water increases down the group because ionisation energies decrease
Metal + Water –> Metal hydroxide + hydrogen
Metal + Steam –> Metal oxide + Hydrogen

Question 3

Trend in solubilities of hydroxides and sulfates

Answer 3

Hydroxides become more soluble down the group

Sulfates become less soluble down the group

Question 4

Medical uses
Group 2 metals

Answer 4

Magnesium hydroxide as an antacid - neutralises excess stomach acid

Barium sulfate used as a tracer (Barium meals) as barium sulfate is opaque to X-rays

Question 5

Agricultural uses group 2 metals

Answer 5

Calcium hydroxide neutralises acid in soil as it is basic

Ionic equation for neutralisation
H+ + OH- –> H2O(l)

Question 6

How is Magnesium used in the extraction of Titanium
+ Equation

Answer 6

1. Titanium(IV) oxide is converted to titanium(IV) chloride by heating it with carbon in a stream of chlorine gas
2. Titanium chloride is then purified by fractional distillation
3. Titanium chloride is then reduced by Magnesium in a furnace at almost 1000 degrees
   Displacement reaction
   2Mg(l) + TiCl4(g) –> Ti(s) + 2MgCl2(l)

Question 7

What happens to the melting point as you go down group 2?

Answer 7

Melting point decreases

• The metal ions get bigger but the number of delocalised electrons per atom doesn’t change (2).
• The larger the atomic radius the further away the delocailsed electrons from the positive nuclei and the less attraction they feel.
• So it takes less energy to break the bond.

Question 8

What happens to the first ionsiation energy as you go down the group 2?

Answer 8

First ionisation energy decreases

• Each element down the Group 2 has an extra electron shell
• The extra inner shells shield the out electrons from the attraction of the nucleus
• The extra shell also means the electrons are further away, greatly reducing the nucleus’s attraction
• This means it is easier to remove the outer electron.

Question 9

What happens to the reactivity as you go down group 2?

Answer 9

It increases

• As you go down the group the first ionisation energy decreases due to increasing atomic radius and shielding
• When they react they lose 2 electrons forming positive ions.
• The easier it is to lose the electron the more reactive the element.

Question 10

Test for sulfate ions

Answer 10

1. Acidify solution by adding hydrochloric acid to get rid of any sulfites and carbonates which also produce a white precipitate.
2. Add acidified barium chloride - white precipitate should form

Ba2+(aq) + SO4 2-(aq) –> BaSO4 (s)

Question 11

Method of removal of sulfur dioxide from atmosphere

Answer 11

Spray with a slurry using either powered calcium oxide or calcium carbonate with water