3.2.2 - group 2, the alkaline earth metals

Question 1

what observations would you make when the group 2 elements react with water?

Answer 1

fizzing (more vigorous down group)
metal dissolving (faster down group)
solution heating up (more down group)
with calcium a white precipitate appears (less precipitate going down group)

Question 2

what products are formed when the group 2 elements react with water?

Answer 2

the aqueous metal hydroxide (which makes the solution alkaline if it is soluble)
hydrogen gas

Question 3

what observations would you make when magnesium reacts with steam?

Answer 3

magnesium will burn with a bright white flame
a white solid will form

Question 4

what products are formed when magnesium reacts with steam?

Answer 4

solid magnesium oxide
hydrogen gas

Question 5

what is the trend in the relative solubilities of the group 2 hydroxides in water?

Answer 5

the group 2 hydroxides become more soluble as you go down the group

Question 6

how do group 2 hydroxides appear if they are not soluble?

Answer 6

as white precipitates

Question 7

what is magnesium hydroxide known as?

Answer 7

sparingly soluble

Question 8

how is magnesium hydroxide used in medicine?

Answer 8

to neutralise excess acid in the stomach (Mg(OH)2 + 2HCl -> MgCl2 + 2H2O) and treat constipation - it is safe because it is so weakly alkaline, and preferable to calcium carbonate as it doesn’t produce CO2 gas

Question 9

how is calcium hydroxide used in agriculture?

Answer 9

to neutralise acidic soils

Question 10

what is the trend in the relative solubilities of the group 2 sulphates in water?

Answer 10

the group 2 sulphates become less soluble as you go down the group

Question 11

what is barium sulphate?

Answer 11

insoluble

Question 12

how is barium sulphate used in medicine?

Answer 12

it is given to patients who need x-rays of their intestines - the barium absorbs the x-rays so the gut appears on the image (barium compounds are toxic but safe here as barium sulphate is insoluble so isn’t absorbed into the blood)

Question 13

what is used to test for sulphate ions?

Answer 13

acidified barium chloride solution

Question 14

what happens when acidified barium chloride solution is added to a solution containing sulphate ions?

Answer 14

a white precipitate forms

Question 15

what is the barium chloride acidified with and why?

Answer 15

hydrochloric acid to react with carbonate impurities (would form white barium carbonate precipitate giving false result)
can’t use sulfuric acid as it contains sufate ions so would give false result

Question 16

what is the trend in atomic radius?

Answer 16

increases down the group because each atom has one more energy level than the last

Question 17

what is the trend in 1st IE?

Answer 17

decreases down the group because the atomic radius increases and the outer electrons are more shielded by inner energy levels

Question 18

what is the trend in melting point?

Answer 18

decreases down the group because the electrostatic forces of attraction (metallic bonding) between the positive ions and delocalised electrons become weaker as the distance between them increases

Question 19

what can magnesium be used for?

Answer 19

to extract titanium from titanium chloride (TiCl4)

Question 20

what are the steps and equations involved in extracting titanium?

Answer 20

1. solid TiO2 is converted to liquid TiCl4 at 900 degrees (TiO2 + 2 Cl2 + 2 C -> TiCl4 + 2 CO)
2. the TiCl4 is purified by fractional distillation in an argon atmosphere
3. the Ti is extracted by Mg in an argon atmosphere at 500 degrees (TiCl4 + 2Mg -> Ti + 2 MgCl2)

Question 21

what can calcium oxide or calcium carbonate be used for?

Answer 21

to remove sulfur dioxide from flue gases, the waste gases from furnaces (flue gas desulfurisation)
SO2 + CaO -> CaSO3