group 2 Flashcards
State and explain the trend in atomic radius down group 2
Radius increases as the number of filled electron shells increases down the group
(note this is not linear, as the nuclear charge increases the pull on the outer shell
increases)
State and explain the trend in 1 st ionisation energy down group 2
1 st ionisation energy decreases down the group. Electron shielding and radius increases
down the group, therefore electrostatic attraction between nucleus and outer electron
shell decreases meaning it is easier to remove the outer electron
State and explain the trend in melting point down group 2
Melting point decreases down the group (with exception of Mg which is lower than
expected). This is because as size of ion increases the distance between nucleus and
delocalised electron field increases meaning a weaker electrostatic attraction requiring
less energy to overcome
Write a general equation for the reaction of Ca, Sr or Ba with water
M(s) + 2H 2 O(l) M(OH) 2 (s) + H 2 (g)
How is the reaction of Mg with water different than that of Ca, Sr
or Ba with water
Mg will only react with steam not liquid water H 2 O(g) not H 2 O(l))
Describe the reaction of Mg with steam and write an equation
A bright white flame is observed, producing a white solid MgO
Mg(s) + H 2 O(g) —-> MgO(s) + H 2 (g)
Explain why very clean Mg will have a slow reaction with water
Mg contains an oxide layer that prevents it reacting with water
Cleaning the Mg removes the oxide layer
Explain how Mg is used to extract titanium from its ore (rutile)
TiO 2 + 2Cl 2 + 2C —> TiCl 4 + 2CO
TiCl 4 + 2Mg —> Ti + 2MgCl2
Mg is used as the reducing agent rather than C, because carbon reduction also produces
titanium carbide (TiC) which is brittle
Write a general simplest ionic equation for the reaction of aqueous
group 2 ions with sodium hydroxide solution
group 2 ions with sodium hydroxide solution
M 2+ (aq) + 2OH - (aq) –> M(OH)2
state of product depends on solubility of hydroxide
State the trend in solubility of hydroxides of group 2
Increases down the group Mg(OH) 2 is insoluble (s), Ba(OH) 2 is soluble (aq)
Give a use of Mg(OH)2 in medicine
Milk of magnesia, neutralises excess stomach acid (antacid tablets)
Give a use of Ca(OH) 2 in agriculture
Used to neutralise acidic soils for growing crops
How are CaO and CaCO 3 used to remove acidic flue gases (SO 2 )
from coal burning emissions?
Flue gases bubbled through a slurry of CaO or CaCO 3 . Produces a precipitate
CaO + SO2 —> CaSO3
CaCO3 + SO2 —-> CaSO 3 + CO2
Write the simplest ionic equation for the reaction of acidified
barium chloride with sulfate ions or sulfuric acid and give an
observation
Ba 2+ (aq) + SO 4 2- (aq) —> BaSO 4 (s)
White precipitate formed
State the trend in solubility of the group 2 sulfates
Decrease in solubility down the group
MgSO 4 is soluble (aq), BaSO 4 is insoluble (s)
