Chapter 9 - Group 2, Alkaline Earth Metals

Question 1

What uses do barium sulfate and magnesium hydroxide and sulfate have?

Answer 1

They all have medical applications, for example barium sulfate is completely insoluble and is given to patients whos GI tract is X-rayed and Magnesium hydroxide is an indigestion cure (milk of magnesia)

Question 2

Which group 2 compound is used in agriculture?

Answer 2

Calcium hydroxide is used to change soil pH

Question 3

Atomic radius trends in group 2:

Answer 3

Increases as you go down (more shells = larger radius)

Question 4

Ionisation energy:

Answer 4

Decreases as you go down the group, more shielding reduces force of attraction between nucleus and outer electrons, easier to lose them

Question 5

Melting point:

Answer 5

Decreases as you go down the group because the nucleus becomes further away from the electron sea. However magnesium has the lowest melting point, so the trend starts from calcium.

Question 6

What are the reactions of group 2 metals between magnesium and barium?

Answer 6

The majority of the metals will react with cold water even magnesium (albeit slowly) to form a metal hydroxide, they also will all react with steam to form their metal oxides, which can then be reacted with water to form the hydroxide in a highly exothermic reaction

Question 7

Uses of magnesium in industry:

Answer 7

Magnesium will react with processed titanium chloride to form magnesium chloride and titanium metal, purifying titanium
2Mg + TiCl4 -> MgCl2 + Ti

Question 8

The use of calcium in industry?

Answer 8

Calcium Oxide or Calcium Carbonate can both react with flue gases (sulfurous by-products of combustion) to remove the sulfur oxides from the air and prevent acid rain, forming gypsum instead which has applications in contruction (plasterboard)

Question 9

Uses of barium in chemical testing:

Answer 9

Soluble barium chloride will react with sulfates to form insoluble barium sulfate, however the solution must first be acidifed because barium will also react with other ions, such as carbonates. This test can also be done the other way to test for chlorides.

Question 10

Trends in solubility of the group 2 hydroxides?

Answer 10

The group 2 hydroxides become more soluble as you go down the group (barium hydroxide is easily soluble whereas calcium hydroxide is sparingly soluble)

Question 11

Trends in solubility of group 2 sulfates?

Answer 11

They become less soluble as you go down the group, with barium sulfate being virtually insoluble.