Group 2 Properties Flashcards
Which Group 2 Ions Have a WHITE PRECIPITATE in OH-
Mg2+
Ca2+
Which Group 2 Ions have a WHITE PRECIPITATE in SO4 2-
Sr2+
Ba2+
Trend in Atomic Radius for group 2
radius increases down the group
more shells of electrons
Trend in melting point down group 2
melting point decreases down the group
metallic bonding weakens
distance between positive ions and delocalised electrons increases
FoA decrease
Trend in first ionisation energy down group 2
decreases down the group more shielding further from nucleus lower FoA less energy to remove electron
Trend in reactivity down group 2
reactivity increases down the group
Group 2 reaction with oxygen using Mg as example
Mg burns with a bright white flame
Produces a metal oxide (MgO) which is a white ionic solid with a high MP
Layer of metal oxide coating the outside must be removed with emery paper before reaction with magnesium ribbon
Magnesium reaction with steam
Produces magnesium oxide and hydrogen
Burns with a bright white flame
Magnesium reaction with warm water
produces magnesium hydroxide Mg(OH)2 and hydrogen
Slow reaction without a flame
Group 2 metal reaction with cold water
Reacts vigorously
Forms metal hydroxides EG) X(OH)2
and hydrogen
Observations for group 2 metal reaction with cold water
Fizzing (More vigorous down group)
Dissolving (More vigorous down group)
Solution heating up (More down group)
A white precipitate appearing with calcium (Less precipitate down group)
What do the metal hydroxides do to the water’s pH
Make it alkaline (If they’re water soluble)
Steps in extracting titanium with magnesium
1) TiO2 converted to TiCl2 (900 degrees c)
TiO2 + 2Cl2 +2C= TiCl4 + 2CO
2) TiCl2 purified through fractional distillation
3) Ti extracted with Mg in argon atmosphere at 500 degrees
TiCl4 + 2Mg = Ti + 2MgCl2
Magnesium Hydroxide
Insoluble in water Mg2+ + 2OH- = Mg(OH)2 pH 9 = slightly dissolved OH- Mg(OH)2 used in medicine to neutralise excess stomach acids Mg(OH)2 +2HCl = MgCl2 + 2H2O
Calcium Hydroxide
Partially in soluble Ca2+ + 2OH- = Ca(OH)2 pH 11= more OH- ions dissolved Used to test for CO2 Ca(OH)2 + CO2 = CaCO3 + H2O
Barium Hydroxide
Fully Soluble
Ba2+ + 2OH- = Ba(OH)2
Strongly alkaline
Ba(OH)2 + aq = Ba2+ + 2OH-
Trend in solubility of sulphates in group 2
solubility decreases down the group
Trend in solubility of group 2 hydroxides
solubility increases down the group
Sulphate ion
SO4 2-
Where is barium sulphate used
X ray of intestines
low solubility stops it from being absorbed into bloodstream
How is BaCl2 used to test for sulphate ions
BaCl2 solution acidified with HCl used as a reagent
Barium sulphate is made (White precipitate)
Ba2+ + SO4 2- = BaSO4
Why is barium sulphate acidified with HCl
Salts often have carbonate impurities, barium carbonate also has a white precipitate so it can be confused for sulphate.
HCl reacts with CO3
Fizzing due to CO2 product
