[8.1] group 2

Question 1

what happens when group 2 metals react with oxygen?

Answer 1

2M (s) + O₂ (g) -> 2MO (s)

• metal is oxidised (from 0 to 2+)
• oxygen is reduced (from 0 to 2-)

Question 2

what happens when group 2 metals react with water?

Answer 2

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

• metal is oxidised (from 0 to 2+)
• H is reduced (from 1+ to 0)

Question 3

what happens when group 2 metals react with acid?

Answer 3

M (s) + 2HCl (aq) -> MCl₂ (aq) + H₂ (g)

• metal is oxidised (from 0 to 2+)
• H is reduced (from 1+ to 0)

Question 4

what is the reactivity trend down group 2?

Answer 4

the metals become more reactive down the group

Question 5

how does solubility of hydroxides change down the group?

Answer 5

• solubility increases down the group
• results in solution containing more OH⁻ (aq) ions
• pH increases
• alkalinity increases

Question 6

how does thermal decomposition of group 2 carbonates change down the group?

Answer 6

• group 2 carbonates become more stable to thermal decomposition going down the group
• SrCO₃ and BaCO₃ do not decompose
• CaCO₃ -> CaO + CO₂

Question 7

what are 2 uses of group 2?

Answer 7

• used to increase the pH of soil (in agriculture by farmers)
• indigestion tablets

Question 8

how is group 2 used to increase the pH of soil?

Answer 8

• soil is acidic
• slaked lime is added, which is calcium hydroxide
• neutralisation reaction occurs, so pH is increased from original acidic state
• Ca(OH)₂ (s) + 2H⁺ (aq) -> Ca²⁺ (aq) + 2H₂O (l)

Question 9

how is group 2 used for indigestion tablets?

Answer 9

• milk of magnesia (Mg(OH)₂) or calcium carbonate
• a neutralisation reaction occurs
• Mg(OH)₂ (s) + 2HCl (aq) -> MgCl₂ (aq) + 2H₂O (l)
• CaCO₃ (s) + 2HCl (aq) -> CaCl₂ (aq) + H₂O (l) + CO₂ (g)