I1: 9 Group 2, the Alkaline Earth Metals Flashcards
What is the trend in atomic radius as you go down Group 2?
Atomic radius increases because the number of shells increases.
What is the trend in first ionisation energy as you go down Group 2?
First ionisation energy decreases because shielding increases so the outer electron is further from the attractive nuclear charge.
What is the trend in melting point as you go down Group 2?
Melting points decrease because the ions get larger but the number of delocalised electrons stay the same. The delocalised electrons are further away from the attractive nuclear charge so the metallic bonding is weaker.
What is the reaction of Mg with water?
What observations are there?
Mg (s) + 2H2O (l) -> Mg(OH)2 (aq) + H2 (g)
Slow reaction with no flame.
What is the reaction of Mg with steam?
What observations are there?
Mg (s) + H2O (g) -> MgO (s) + H2 (g)
Burns brightly with a white flame and a white solid is produced.
What is the reaction of Ca with water?
What observations are there?
Ca (s) + 2H2O (l) -> Ca(OH)2 (aq) + H2 (g)
Fizzing, metal dissolves, solution heats up, white precipitate.
What is the reaction of Sr with water?
What observations are there?
Sr (s) + 2H2O (l) -> Sr(OH)2 (aq) + H2 (g)
Fizzing, metal dissolves, solution heats up.
What is the reaction of Ba with water?
What observations are there?
Ba (s) + 2H2O (l) -> Ba(OH)2 (aq) + H2 (g)
Fizzing, metal dissolves, solution heats up.
What is the trend in reactivity with water as you go down Group 2?
Reactivity increases due to the decrease in first ionisation energy.
How is magnesium used in the extraction of titanium?
TiO2 (the main titanium ore) is first converted to TiCl4 by heating with carbon in a stream of chlorine gas.
The TiCl4 is then purified by fractional distillation, before being reduced by Mg in a furnace at almost 1000 degrees.
TiCl4 (g) + 2Mg (l) -> Ti (s) + 2MgCl2 (l)
What is the trend in solubility down the Group 2 hydroxides?
Solubility increases.
Mg(OH)2 is sparingly soluble.
What is the trend in solubility down the sulfates of Group 2?
Solubility decreases.
BaSO4 is insoluble.
How is Mg(OH)2 used in medicine?
It’s used as a suspension in milk of magnesia to neutralise stomach acid.
It’s only sparingly soluble so won’t be absorbed by the body.
How is Ca(OH)2 used in agriculture?
It’s used as slaked lime to neutralise acidic soils.
How is CaO or CaCO3 used to remove SO2 from flue gases?
Wet scrubbing - the acidic sulfur dioxide can be removed from flue gases by reacting with an alkali.
Powdered calcium oxide (CaO) and calcium carbonate (CaCO3) can both be used.
A slurry is made by mixing the CaO or CaCO3 with water which is then sprayed onto the flue gases. The sulfur dioxide reacts with the alkaline slurry and produces calcium sulfite.
CaO (s) + 2H2O (l) + SO2 (g) -> CaSO3 (s) + 2H2O (l)
CaCO3 (s) + 2H2O (l) + SO2 (g) -> CaSO3 (s) + 2H2O (l) + CO2 (g)
