group 2 -paper 1

Question 1

State and explain the trend in atomic radius down group 2

Answer 1

-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)

Question 2

State and explain the trend in 1 st ionisation energy down group 2

Answer 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

Question 3

State and explain the trend in melting point down group 2

Answer 3

-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

Question 4

Write a general equation for the reaction of Ca, Sr or Ba with water

Answer 4

X(s) + 2H 2 O(l) —> X(OH) 2 (s) + H 2 (g)

Question 5

How is the reaction of Mg with water different than that of Ca, Sr or Ba with water

Answer 5

Mg will only react with steam not liquid water (H2O(g) not H2O(l))

Question 6

Describe the reaction of Mg with steam and write an equation

Answer 6

-A bright white flame is observed,
-producing a white solid MgO

Mg(s) + H 2 O(g)  MgO(s) + H 2 (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 (rutile)

Answer 8

TiO 2 + 2Cl 2 + 2C —>TiCl 4 + 2CO
TiCl 4 + 2Mg —>Ti + 2MgCl 2
-Mg is used as the reducing agent rather than C, because carbon reduction also produces
titanium carbide (TiC) which is brittle

Question 9

Write a general simplest ionic equation for the reaction of aqueous
group 2 ions with sodium hydroxide solution

Answer 9

M 2+ (aq) + 2OH - (aq) —>M(OH)2
-state of product depends on solubility of hydroxide

Question 10

State the trend in solubility of hydroxides of group 2

Answer 10

Increases down the group Mg(OH) 2 is insoluble (s), Ba(OH) 2 is soluble (aq)

Question 11

Give a use of Mg(OH) 2 in medicine

Answer 11

-Milk of magnesia,
-neutralises excess stomach acid (antacid tablets)

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 CaCO 3 used to remove acidic flue gases (SO2)from coal burning emissions?

Answer 13

-Flue gases bubbled through a slurry of CaO or CaCO 3 . -Produces a precipitate
CaO + SO 2 –> CaSO 3
CaCO 3 + SO2 –> CaSO 3 + CO 2

Question 14

Write the simplest ionic equation for the reaction of acidified barium chloride with sulfate ions or sulfuric acid and give an observation

Answer 14

Ba2+ (aq) + SO4 2- (aq) –>BaSO4(s)
-White precipitate formed

Question 15

State the trend in solubility of the group 2 sulfates

Answer 15

Decrease in solubility down the group

Question 16

Explain why barium chloride solution used to test for sulfate ions must be acidified

Answer 16

-Prevents the formation of a white ppt of BaCO3
-This is formed when atmospheric CO 2 dissolves 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 meal.
-It is dense and reflects X-rays
-Insoluble and therefore non-toxic and cannot be absorbed into the blood