Group 2

Question 1

Atomic radius and ionisation energy

Answer 1

Atomic radius increases down a group.
First ionisation energy decreases due to increased distance and shielding.

Question 2

Melting point

Answer 2

Melting point decreases generally down the group except for magnesium which is the lowest of them all.

Question 3

Extracting titanium ore

Answer 3

TiO2 +2Cl2 + 2C ——> TiCl4 + 2CO

TiCl4 + 2Mg ——> Ti + 2MgCl2
(Magnesium reacts as a reducing agent)

Reacting magnesium with carbon (usual method of extraction) produces a carbide which is too brittle to be useful

Question 4

Preventing acid rain

Answer 4

Burning fossil fuels gives off sulfur dioxide which causes acid rain.
This can be prevented by spraying a slurry of calcium oxide or calcium carbonate over the sulfur dioxide gas, collecting the calcium sulfite that forms.

Question 5

Reactivity with water

Answer 5

React with water to form hydroxides.
Down group 2 reactions become more vigorous with water due to lower activation energy.
At room temperature magnesium hardly reacts with water but rapidly reacts with steam to form magnesium oxide and hydrogen. (Bright light)

Question 6

Solubility of hydroxides

Answer 6

Increases down the group.
Magnesium hydroxide is barely soluble so appears as white precipitate.

Question 7

Solubility of sulfates

Answer 7

Decreases down the group.
Barium sulfate is almost insoluble in water (hence why used for barium meal)

Question 8

Testing for sulfate ions

Answer 8

React barium chloride with solution if white ppt forms sulfate is present. To ensure it is not barium carbonate first add acid to solution to remove any carbonate ions