2.2.3 Reactions of Group 2

Question 1

Reactions with Be, Mg, Ca, Sr and Ba with water?

Answer 1

Be - no reaction
Mg - None with water, but vigorous with steam
Ca - Moderately reacts with water, hydroxide formed
Sr - Reacts rapidly with water, hydroxide formed
Ba - Reacts vigorously with water, hydroxide formed

Question 2

Reactions of Ba, Mg, Ca, Sr and Ba with oxygen?

Answer 2

Be - reluctant to burn but white flame
Mg - Burns easily, white bright flame
Ca - Difficult to ignite but red flame
Sr - Difficult to ignite but red flame
Ba - Difficult to ignite but green flame

Question 3

Reactions of Be, Mg, Ca, Sr and Ba with dilute HCL?

Answer 3

Be - Rapidly reacts
Mg - Vigorously reacts
Ca - Vigorously reacts
Sr - Vigorously reacts
Ba - Vigorously reacts

Question 4

Reactions of Be, Mg, Ca, Sr and Ba with dilute H2SO4?

Answer 4

Be - Vigorous
Mg - Vigorous
Ca - Slowed by formation of soluble sulfate later covering metal, stopping H2 bubbles from rising
Sr - Reaction stopped by layer of sulfur which is insoluble on metals surface
Ba - Stopped by formation of insoluble sulfate layer on metals surface

Question 5

General equation for group 2 reacting with oxygen?

Answer 5

2M (s) + O2 (g) → 2MO (s)

Sr and Ba form peroxides MO2

Question 6

General equation for group 2 reacting with water?

Answer 6

M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)

Except Be which doesn’t react with water

Question 7

How does Mg react with cold water? What about with steam?

Answer 7

• Very slowly
• Weakly alkaline solution formed (Mg(OH)2 only slightly soluble)
• With steam, vigorously reacts
• Mg (s) + H2O (g) → MgO (s) + H2 (g)

Remember it forms an oxide here not a hydroxide

Question 8

How do group 2 metals react with dilute acids?

Answer 8

M (s) + 2HCl (aq) → MCl2 (aq) + H2 (g)

M (s) + H2SO4 (aq) → MSO4 (aq) + H2 (g)

• Form colourless solutions of metal salts
• Soluble salt forms in HCL, increasing in solubility down group 2
• Some soluble and some insoluble (SrSO4 and BaSO4) salts form, decreasing in solubility down group in H2SO4

Question 9

Group 2 oxide notes

Answer 9

• Group 2 oxides are basic
• Except BeO which is amphoteric (can act as an acid and a base)
• React with water forming alkaline solutions, becoming more alkaline going down group
• Oxide + water = hydroxide
• CaO = Limewater
• Oxide + dilute hydrochloric acid → chloride + water
• Oxide + dilute sulfuric acid → sulfate + water
  (these sulfates decrease in solubility down the group (BaSO4 and SrSO4 are insoluble))
• Prevented by using oxide powder and stirring so neutralisation can take place

Question 10

Reaction of group 2 Hydroxide notes

Answer 10

• Colourless solutions of metal salts when reacted with dilute acid

hydroxide + dilute hydrochloric acid → chloride + water

hydroxide + dilute sulfuric acid → sulfate + water

Question 11

Reactions of group 2 carbonates notes

Answer 11

BeCO3 soluble, everything else is not

carbonate + dilute hydrochloric acid → chloride + water + carbon dioxide
( salt here is soluble)

carbonate + dilute sulfuric acid → sulfate + water + carbon dioxide
(insoluble salt)
Carbonates of Ca, Sr and Ba form and an insoluble sulfate layer forms on the solid carbonate stopping any further reaction from occurring, after initial bubbling of CO2 is seen