Chapter 9- Group 2, the Alkaline Earth Metals

Question 1

How does atomic radius change down group 2?

Answer 1

Increases going down the group
-nuclear charge increases BUT
-more shells
-more shielding
less attraction between nucleus and outer electrons

Question 2

How does first ionisation energy change down group 2?

Answer 2

Decreases down the group
-more shells
-more shielding
-less attraction between nucleus and outer electrons
less energy required to remove outer electron

Question 3

How does melting point change down group 2?

Answer 3

Decreases down the group
-ionic radius increases due to more shells (in lattice)
-less attraction with delocalised electrons
less energy required to break metallic bonds

Question 4

How does magnesium react with water?

Answer 4

Very slowly with cold water but rapidly with steam to form Mg(OH)2 and H2
-releases bright white light and a white solid is formed

Question 5

How do calcium, strontium and barium react with water?

Answer 5

Calcium reacts similarly to Mg but more vigorously, even with cold water
Strontium and barium react more vigorously still

Question 6

How is magnesium hydroxide used in medicine?

Answer 6

Milk of magnesia: antacid (indigestion remedy) drank to neutralise excess stomach acid (heartburn, indigestion, wind)

Question 7

How is calcium hydroxide used in agriculture?

Answer 7

Slaked lime: treat acidic soil, increasing soil pH. Different plants thrive with different soil pH.

Question 8

How is magnesium used to extract titanium?

Answer 8

Mg (s) + TiCl4 (l) –> MgCl2 (s) + Ti (s)

Question 9

How does the solubility change down the group for hydroxides?

Answer 9

Increases down the group
-Mg(OH)2 is almost insoluble (suspension in water)
-Ca(OH)2 is not that soluble
-Sr(OH)2 is more soluble
-Ba(OH)2 is soluble, dissolves to produce strong alkaline solution

Question 10

How does the solubility change down the group for sulfates?

Answer 10

Decreases down the group
-MgSO4 is soluble
-CaSO4 is quite soluble
-SrSO4 is not that soluble
-BaSO4 is insoluble

Question 11

What is the test for sulfate ions?

Answer 11

-Add nitric acid or HCl to remove carbonate ions as CO2 (as barium carbonate is also a white insoluble solid).
-Add barium chloride solution and if a sulfate is present then a white precipitate is formed.

Question 12

How is barium sulfate used and how is this safe?

Answer 12

Taken by mouth as a barium meal before X-rays to outline the gut and find blockages (Ba absorbs X-rays).
BaSO4 is toxic if it enters the bloodstream, but cannot due to insolubility and so it is safe.

Question 13

How are calcium oxide and calcium carbonate used in flue gas desulfurisation?

Answer 13

React with sulfur dioxide to remove from flue gases and prevent it from polluting the atmosphere