9.2 - Reaction of Group 2

Question 1

Reactions with oxygen going down Group 2 (Mg, Ca, Sr, Ba):

Answer 1

• Mg - burns easily (bright white light) - 2Mg (s) + O2 (g) → 2MgO (s)
• Ca - difficult to ignite (red flame) - 2 Ca (s) + O2 (g) → 2CaO (s)
• Sr - difficult to ignite (red flame) -

2Sr (s) + O2(g) → 2SrO (s)

Sr (s) + O2(g) → SrO2 (s)

• Ba - difficult to ignite (green flame) -

2Ba (s) + O2(g) → 2BaO (s)

Ba (s) + O2(g) → BaO2 (s)

Question 2

Reactions with water going down group 2 (Mg, Ca, Sr, Ba):

Answer 2

• Mg - vigorous reaction with steam and none with water - Mg (s) + H2O (g) → MgO (s) + H2 (g)
• Ca - reacts moderately - forms a hydroxide - Ca (s) + 2H2O (l) → Ca(OH)2(s) + H2 (g)
• Sr - reacts rapidly - forms a hydroxide -

Sr (s) + 2H2O (l) → Sr(OH)2(aq) + H2(g)

Question 3

Reactions with dilute HCl going down group 2

Answer 3

• Mg - reacts vigorously -

Mg (s) + 2HCl (aq) → MgCl2(aq) H2(g)

• Ca - reacts vigorously -

Ca (s) + 2HCl (aq) → CaCl2(aq) H2(g)

• Sr - reacts vigorously -

Sr (s) + 2HCl (aq) → SrCl2(aq) H2(g)

• Ba - reacts vigorously -

Ba (s) + 2HCl (aq) → BaCl2(aq) H2(g)

Question 4

Reaction with dilute H2SO4 going down group 2

Answer 4

• Mg - reacts vigorously
• Ca - reaction slowed by formation of the sparingly soluble sulphate layer on the metal which stops hydrogen bubbles from rising
• Sr - reaction is quickly stopped by the formation of an insoluble sulphate layer on the metal
• Ba - reaction is quickly stopped by the formation of an insoluble sulphate layer on the metal

Question 5

Reaction fo magnesium slowly reacting with water

Answer 5

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

solution formed is weakly alkaline and is slightly soluble

Question 6

Group 2 oxides reacting with water

Answer 6

Question 7

what are all group 2 oxides (acidic or basic):

Answer 7

all group 2 oxides are basic apart from BeO which is amphoteric (can be basic and acidic)

Question 8

Group 2 oxides reacting with acids - why does an oxide stop reacting

Answer 8

• group 2 sulphates can be formed when a group 2 oxide is reacted with sulphuric acid
• insoluble sulphates form at the surface of the oxide which means that teh solid oxide beneath it can’t react with the acid

Question 9

How can the unreactivity be prevented

Answer 9

by stirring and using it within powder form (neutralisation can however occur)

Question 10

Metal oxide + HCl

Answer 10

metal chloride + water

Question 11

Metal oxide + dilute sulphuric acid

Answer 11

metal oxide + dilute sulfuric acid → metal sulfate + water

Question 12

Group 2 metal hydroxide reactions when they react with HCl

Answer 12

colourless solutions of metal salts are formed

Question 13

reaction of group 2 hydroxides with dilute acids (HCl and H2SO4)

Answer 13

Question 14

Reactions of group 2 carbonates (solubility):

Answer 14

all are insoluble apart from BeCO3
carbonates of Ca, Sr and Ba form as an insoluble sulphate layer on their solid carbonates which stops any further reaction after the initial effervesence of CO2

Question 15

Group 2 carbonates reacting with dilute acids

Answer 15

carbonate + dilute hydrochloric acid → chloride + water + carbon dioxide

carbonate + dilute sulfuric acid → sulfate + water + carbon dioxide