3.2.2 Group 2, the Alkaline Earth Metals

Question 1

What are the trends in atomic radius of the elements Mg-Ba?

Answer 1

The atomic radius increases. This is due to nuclear charge increasing but also shielding increasing so attraction between nucleus and valence electrons decreases.

Question 2

What are the trends in first ionisation energy of the elements Mg-Ba?

Answer 2

First ionisation energy decreases due to nuclear charge increasing, atomic radius increasing, shielding increasing and so attraction decreasing which makes it easier to remove valence electron

Question 3

what is the trends in reactivity of the elements Mg-Ba?

Answer 3

Reactivity increases

Question 4

what are the trends in melting point of the elements Mg-Ba?

Answer 4

Melting point decreases due to nuclear charge increases, atomic radius increases, shielding increases, so attraction decreases making the metallic bonding weaker.

Question 5

What is Be reaction with water? Observations

Answer 5

doesnt react at all with water at room temperature

Question 6

What is Mg reaction with water? Observations

Answer 6

Mg reacts slowly with cold water. But reacts vigorously with steam. White flame, white powder

Question 7

What is Ca reaction with water? Observations

Answer 7

Reacts with water - fizzing, slow, white precipitate forms

Question 8

What is Sr reaction with water? Observations

Answer 8

reacts with water, vigorous fizzing, colourless solution

Question 9

What is Ba reaction with water? Observations

Answer 9

Reacts with water - even more vigorous fizzing, colourless

Question 10

Explain use of magnesium in the extraction of titanium from TiCl4.

Answer 10

Mg is used to reduce titanium tetrachloride to produce titanium metal (extract titanium from its ore).

Question 11

Explain the use of calcium compounds.

Answer 11

Can be used to remove sulfur dioxide released from fossil fuels before turning into acid rain.

Question 12

What is the relative solubilities of hydroxides of the elements Mg-Ba in water?

Answer 12

Solubility increases down the group. Mg(OH)2 sparingly soluble

Question 13

Why is Mg(OH)2 sparingly soluble?

Answer 13

Due to its relatively low hydration enthalpy compared to the other hydroxides in the group.

Question 14

How is Mg(OH)2 used in medicine?

Answer 14

used as an antacid to neutralise excess stomach acid

Question 15

How is Ca(OH)2 used in agriculture?

Answer 15

used to adjust soil pH and provide essential calcium nutrients to plants

Question 16

Explain the use of CaO or CaCO3 to remove SO2 from flue gases.

Answer 16

used to react with SO2 in flue gases to form calcium sulfite/ sulfate, which can be easily removed from the gas stream

Question 17

What are the relative solubilities of the sulfates of the elements Mg-Ba in water?

Answer 17

Solubility decreases. BaSO4 is insoluble

Question 18

Why is BaSO4 insoluble?

Answer 18

due to its high lattice energy, making it difficult for water molecules to overcome the strong attractions between the ions in the solid lattice

Question 19

How is barium chloride used to test for sulphate ions?

Answer 19

Add dilute hydrochloric acid and barium chloride to a solution containing sulfate ions.

White precipitate of barium sulfate is formed

Question 20

Why is acidified BaCl2 solution used to test for sulphate ions?

Answer 20

helps prevent the precipitation of other metal hydroxides or carbonates

Question 21

Explain the use of BaSO4 in medicine.

Answer 21

contrast medium for X-rays imaging of the gastrointestinal tract due to its insolubility and radiopacity, allowing for clear visualisation of the digestive system

Question 22

Why is HCL added to barium chloride to test for sulfates.

Answer 22

HCL contains chloride ions
These will react with any carbonates and impurities and remove them