Group 2

Question 1

Group 2 elements + oxygen

Answer 1

2M + O(2) -> 2MO, where M is any group 2 element. The group 2 element is oxidised, while the oxygen is reduced

Question 2

Group 2 elements + water

Answer 2

2M + 2H(2)O -> 2M(OH)2 + H(2), where M is any group 2 element. The group 2 element is oxidised, while one of the hydrogen atoms in each water molecule is reduced (the oxygen and other hydrogen don’t change)

Question 3

Trend in reactivity down group 2

Answer 3

Increases, due to increasing ease of forming cations (losing electrons) as the atomic radii increases, along with the electron shielding. The effect of increase in nuclear charge is outweighed by these.

Question 4

Water + group 2 oxides

Answer 4

MO + H(2)O -> M(OH)2 , where M is any group 2 element. Typical pH may be 10-12
M(OH)2 + aq -> M^2+ + 2OH^-
Solubility of hydroxides in water increases as go down group - Mg(OH)2 is only slightly soluble, with a relatively low OH- concentration, while Ba(OH)2 is much more soluble, with a greater OH- ion concentration and a more alkaline solution

Question 5

Thermal decomposition of group 2 carbonates

Answer 5

MCO(3) -> MO + CO(2), where M is any group 2 element. Carbonates become more difficult to decompose as you go down the group, needing higher temperatures

Question 6

Use of Ca(OH)2 in agriculture

Answer 6

As lime to neutralise acid soils

Question 7

Use of Mg(OH)2 in medicine

Answer 7

Used in milk of magnesia to relieve indigestion. Neutralises excess stomach acid (as an antacid).

Question 8

Draw diagram of all reactions of calcium, including Ca, CaO, Ca(OH)2, CaCO3 and Ca(HCO3)2

Answer 8

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