Module 2: Group 2 (Alkaline Earth Metals)

Question 1

What is the trend in atomic radius down group 2 & why?

Answer 1

• Increases
• Atomic number increases & shielding increases.
• Extra electron shells are added increasing distance between nucleus & outer electrons.

Question 2

What is the trend in first ionisation energy down group 2 & why?

Answer 2

• Decreases
• Each element has an extra electron shell compared to the one above (greater atomic radius).
• Electrons lost more easily due to increased shielding.
• Electrostatic attraction between nucleus & outer electrons decreases.
• The increasing positive charge of nucleus (due to extra protons) is overridden by the effect of the extra shells.

Question 3

What is the trend in reactivity down group 2 & why?

Answer 3

• Increases
• React to lose electrons & form positive ions.
• Energy needed to form positive ions falls due to decrease in ionisation energy.
• Leads to lower Ea & faster reactions.

Question 4

What is the trend in melting point down group 2 & why?

Answer 4

• Decreases
• Greater shielding & atomic radius offsetting greater nuclear charge.
• Metal ions increase in size so less energy required to break metallic bonds.
• Weaker electrostatic forces of attraction between positive ions & delocalised electrons.
• Drop with Mg as sudden change in crystal structure.

Question 5

What is the type of bonding found between group 2 atoms?

Answer 5

Metallic bonding

Question 6

What is the trend in reactivity of group 2 metals with water?

Answer 6

• Increase.
• React with increasing vigour.
• Ionisation energy decreases.

Question 7

What is produced when group 2 metals react with water?

Answer 7

Metal hydroxide & hydrogen

Question 8

What is the general reaction for a group 2 metal with water?

Answer 8

M (s) + 2H2O (l) –> M(OH)2 (aq) + H2 (g)

Question 9

What is the reaction of Mg with cold water?

Answer 9

Mg (s) + 2H2O (l) –> Mg(OH)2 (aq) + H2 (g)

Question 10

How does Mg react with cold water?

Answer 10

Very slowly

Question 11

How does Mg react with steam

Answer 11

Rapidly

Question 12

What is the reaction of Mg with steam?

Answer 12

Mg (s) + H2O (g) –> MgO (s) + H2 (g)

Question 13

What is the reaction of MgO with cold water?

Answer 13

MgO (s) + H2O (l) –> Mg(OH)2 (aq)

Question 14

What is the reaction of Ca with cold water?

Answer 14

Ca (s) + H2O (l) –> Ca(OH)2 (aq) + H2 (g)

Question 15

What is the reaction of Mg with dilute HCl?

Answer 15

Mg (s) + HCl (aq) –> MgCl2 (aq) + H2 (g)

Question 16

What is the reaction of Ca with dilute H2SO4?

Answer 16

Ca (s) + H2SO4 (aq) –> CaSO4 (s) + H2O (l)

Question 17

What is observed when Mg is reacted with dilute HCl?

Answer 17

• Exothermic reaction
• Vigorous bubbling
• Effervescence
• Warm test tube
• White precipitate

Question 18

What is observed when Mg is reacted with dilute H2SO4?

Answer 18

• Exothermic reaction
• Hydrogen gas given off

Question 19

What is observed when Ca is reacted with dilute HCl?

Answer 19

• Exothermic reaction
• Effervescence
• Warm test tube
• Vigorous reaction

Question 20

What is observed when Ca is reacted with dilute H2SO4?

Answer 20

• Exothermic reaction
• White precipitate
• Limited reaction

Question 21

Why is their a limited reaction when Ca reacts with H2SO4 compared to Mg?

Answer 21

CaSO4 is less soluble compared to MgSO4.

Question 22

What is the trend in solubility of hydroxides?

Answer 22

Solubility increases down the group.

Question 23

What is the least soluble hydroxide?

Answer 23

Mg(OH)2

Question 24

What is the most soluble hydroxide?

Answer 24

Ba(OH)2

Question 25

What is the trend in solubility of sulfates?

Answer 25

Solubility decreases down the group.

Question 26

What is the solubility of Mg(OH)2 in water?

Answer 26

Sparingly soluble

Question 27

What is the solubility of BaSO4 in water?

Answer 27

Insoluble in water

Question 28

What is the use of BaSo4?

Answer 28

- Used in medicine as barium meals. - Aid in diagnosing problems with oesophagus, stomach or intestines. - Insoluble, so can't be absorbed into the bloodstream.

Question 29

What is the test for sulfate ions?

Answer 29

- Add dilute HCl. - Add solution of BaCl2 - If sulfate is present, white precipate is produced. - Ba2+ (aq) + SO4^2- (aq) --> BaSO4 (s)

Question 30

Why is dilute HCl added when testing for sulfates?

Answer 30

To remove any carbonate ions present that may disrupt results & form a white precipitate of BaCO3.

Question 31

What is the process of using Mg to extract Ti from its ore?

Answer 31

- Titanium (IV) oxide (TiO2) is converted to titanium (IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas. - TiCl4 is then purified by fractional distillation. - Then reduced by magnesium in a furnace at

Question 32

What are the equations for the extraction of Ti using Mg?

Answer 32

- TiO2 (s) + 2Cl2 (g) + 2C (s) --> TiCl4 (g) + 2CO (g) - TiCl4 (g) + 2Mg (l) --> Ti (s) + 2MgCl2 (l)

Question 33

What are the conditions for titanium extraction & why?

Answer 33

- Reaction heated under high temperature & inert conditions. - Mg may react with air & produce inaccurate results

Question 34

Why is titanium more expensive to produce?

Answer 34

- Titanium requires a series of reactions to extract it from its ore. - Made in batches which is time consuming & expensive.

Question 35

What are the properties & use of Mg(OH)2?

Answer 35

- Sparingly soluble. - Sold as 'Milk of Magnesia' in water solution. - Used in indigestion tablets as an antacid to neutralise excess stomach acid.

Question 36

What are the properties & use of Ca(OH)2?

Answer 36

- Sparingly soluble. - Solution used as lime-water. - Used in agriculture to neutralise acidic soils.

Question 37

What is wet scrubbing?

Answer 37

The process of removing acidic sulfur dioxide from flue gases by reacting them with an alkali.

Question 38

Name two alkalis that can be used in wet scrubbing?

Answer 38

- Calcium oxide (Lime, CaO). - Calcium carbonate (Limestone, CaCO3).

Question 39

What is the process of removing SO2 from flue gases (west scrubbing)?

Answer 39

- A slurry is made by mixing CaO or CaCO3 with water. - This is sprayed onto the flue gases. - SO2 reacts with the alkaline slurry to produce a solid, waste product of CaSO3.

Question 40

What are the equations for the removal of SO2 from flue gases (wet scrubbing)?

Answer 40

- CaO (s) + 2H2O (l) + SO2 (g) --> CaSO3 (s) + 2H2O (l). - CaCO3 (s) + 2H2O (l) + SO2 (g) --> CaSO3 (s) + 2H2O (l) + CO2 (g).