group 2

Question 1

state and explain the trend in atomic radius going down group 2

Answer 1

increases as the number of filled electron shells increases down the group

Question 2

state and explain the trend in the first ionisation energy going down group 2

Answer 2

decreases as electron shielding and radius increases down the group, therefore electrostatic attraction between the nucleus and outer electron shell decreases meaning it is easier to remove outer e-

Question 3

state and explain the trend in melting point going down group 2

Answer 3

decreases because the size of the ion increases so the distance between the nucleus and delocalised electron field increases, meaning there is a weaker electrostatic attraction which requires less energy to overcome

Question 4

whats the general equation for the reaction of Ca, Sr or Ba with water?

Answer 4

X(s) + 2H₂O(l) = X(OH)₂(s) + H₂(g)

Question 5

how is the reaction of Mg with water different?

Answer 5

Mg will only react with steam, not liquid water

Question 6

describe the reaction of Mg with steam

Answer 6

a bright white flame is observed which produces a white solid MgO
Mg(s) + H₂O(g) = MgO(s) + H₂(g)

Question 7

explain why very clean Mg will have a slow reaction with water

Answer 7

Mg contains an oxide layer that prevents it reacting with water, cleaning the Mg removes the oxide layer

Question 8

explain how Mg is used to extract titanium from its ore

Answer 8

TiO₂ + 2Cl₂ + 2C = TiCl₄ + 2CO
TiCl₄ + 2Mg = Ti + 2MgCl₂
Mg is used as the reducing agent rather than C because carbon reduction also produces TiC which is brittle

Question 9

whats the simplest ionic equation for the reaction of aqueous group 2 ions with sodium hydroxide solution

Answer 9

M2+(aq) + 2OH-(aq) = M(OH)₂
state of product depends on the solubility of the sodium hydroxide

Question 10

state the trend in solubility of hydroxides of group 2

Answer 10

increases down the group
Mg(OH)₂ is insoluble
Ba(OH)₂ is soluble

Question 11

give a use of Mg(OH)₂ in medicine

Answer 11

milk of magnesia, which neutralises stomach acid

Question 12

give a use of Ca(OH)₂ in agriculture

Answer 12

used to neutralise acidic soils for growing crops

Question 13

how are CaO and CaCO₃ used to remove acidic flue gases from coal burning emissions?

Answer 13

flue gases bubbled through a slurry of CaO or CaCO₃ which produces a ppt
CaO + SO₂ = CaSO₃
CaCO₃ + SO₂ = CaSO₃ + CO₂

Question 14

write the simplest ionic equation for the reaction of acidified barium chloride with sulfate ions or sulfuric acid

Answer 14

Ba2+(aq) + SO₄2-(aq) = BaSO₄(s)
white ppt formed

Question 15

state the trend in solubility of group 2 sulfates

Answer 15

decrease in solubility down the group
MgSO₄ is soluble
BaSO₄ is insoluble

Question 16

explain why barium chloride solution used to test of sulfate ions must be acidified

Answer 16

prevents the formation of white ppt of BaCO₃ which is formed when atmospheric carbon dioxide is dissolved in the solution

Question 17

give a use for barium sulfate in medicine and explain why it is suitable for this purpose

Answer 17

barium metal is dense and deflects xrays, its insoluble and therefore non toxic