3.2 Inorganic Chemistry: .2 Group 2, the alkaline earth metals

Question 1

how many electrons do all group 2 elements have in their outer shell?

Answer 1

2 electrons

Question 2

how does a group 2 element become and ion? and what sort of ion does it become?

Answer 2

it loses 2 electrons to form a

2+ ion

Question 3

what is the trend in atomic radius down the group? why?

Answer 3

• the atomic radius increases down the group

- this is because the elements get bigger getting an extra main energy level compared with the one above it

Question 4

what is the trend in ionisation energy as you go down the group?

Answer 4

• the ionisation energy decreases down the group
• this is because as you go down the group the elements gain an extra shell so the
• outer electron is more shielded from the nucleus
• meaning that the attraction between the nucleus and outer electron get weaker
• therefore less energy is required to remove the outer electron from the atom

Question 5

what is the trend in melting point as you go down the group?

Answer 5

-the melting point generally decreases down the group
this is because;
-going down the group the metal ions get bigger
-the larger the ionic radius the further away the delocalised electrons are from the positive nuclei and the less attraction they feel
-weaker electrostatic force as you go down the group
-so it requires less energy to break the bonds

Question 6

what is produced when Magnesium reacts with water

Answer 6

M(s?) + 2H2O(l)–> M(OH)2(aq) + H2(g)

*this is the same for all reaction just substitute the element

Question 7

does barium react with water?

Answer 7

no

Question 8

what is produced when Magnesium reacts with steam?

Answer 8

Mg + H2O(steam) –> MgO + H2

*this is the same for all reaction just substitute the element

Question 9

what is the trend in solubility with hydroxides going down the group?

Answer 9

the metals hydroxides increase in solubility as you go down the group

(* remember sIngly charged ions e.g [OH-] Increase in solubility)

Question 10

is Magnesium insoluble or soluble in water

Answer 10

• magnesium reacts with water to form Magnesium hydroxide which is almost insoluble (sparingly insoluble)
• (Mg+ and OH-, two small ions hold tight)

Question 11

what is the trend in solubility with Sulfate ions going down the group?

Answer 11

the metal sulfate decrease in solubility down the group

* remember Doubly charged negative ions e.g (SO2-) Decrease in solubility down the group

Question 12

give the ionic equation for the formation of Barium Sulphate and state whether it is soluble or insoluble

Answer 12

Ba2+(aq) + SO42-(aq) –> BaSO4 (s)

-barium sulphate is insoluble

Question 13

describe the test for a sulphate ion and state what you see

Answer 13

• you first acidify the solution with hydrochloric acid or nitric acid to get rid of any sulphites or carbonates (CO32-) which could also produce a white precipitate
  e. g NaCO3 + 2HCL –> 2NaCl + H2O + CO2
• then you add barium chloride solution and if the sulphate is present a white precipitate of barium sulphate is formed

Question 14

I am adding barium chloride to Iron sulphate, produce an equation for this reaction

Answer 14

BaCl2 (aq) + FeSO4 (aq) –> BaSO4 (s) + FeCl2(aq)

Question 15

(edit) I am adding barium Nitrate to Iron sulphate, produce an equation for this reaction

Answer 15

Ba(NO3)2 + FeSO4 (aq) –> BaSO4 (s) + Fe(NO3)3(aq)

Question 16

What is Calcium used for?

Answer 16

Calcium hydroxide [aka slaked lime, aka Ca(OH)2] is used in agriculture to neutralise acid soils

Question 17

what is Magnesium used for? (with water)

Answer 17

Magnesium hydroxide [Mg(OH)2] is used in some indigestion tablets as an antacid- substance that neutralises excess stomach acid

Question 18

what is the ionic equation for neutralisation?

Answer 18

H+ (aq) + OH- (aq) –> H2O (l)

Question 19

what is Barium used for?

Answer 19

• barium reacts with sulphate to produce barium sulphate
• this chemical is used in barium meals
• Barium sulphate is opaque to x-rays so it allows soft tissues to come up on the x-ray picture
• the patient swallows the barium meal, the barium sulphate coats the tissues, making them show up on the x-rays showing the structure of the organ
• helps to diagnose probs with the oesophagus, stomach or intestines

Question 20

what else can magnesium be used for? state the equation

Answer 20

• magnesium can be used in the extraction of Titanium from its ore
• the main titanium ore (TiO2) is converted to titanium chloride (TiCl4) by heating it with carbon in a stream of chlorine gas
• the titanium is then purified by fractional distillation, before being reduced by magnesium in a furnace pf almost 1000 degrees

-TiCl4(g) + 2Mg(l) –> Ti(s) + 2MgCl2(l)

Question 21

what is calcium oxide and calcium carbonate used for?

Answer 21

• sulphur dioxide (a pollutant) is produced when fossil fuels are burnt
• the acidic sulphur dioxide can be removed from flue gases in a process called wet scrubbing
• powdered calcium oxide (lime, CaO) and calcium carbonate (CaCO3) can both be used for this
• a slurry is made by mixing the CaO or calcium carbonate with water
• it’s then sprayed onto the flue gases
• the slurry reacts with the sulphur dioxide to produce Calcium Sulphate

Question 22

give the equation for a slurry made up of calcium oxide reacting with sulphur dioxide

Answer 22

CaO(s) + 2H2O(l) + SO2(g) –> CaSO3(s) + 2H2O(l)

Question 23

give the equation for a slurry made up of calcium carbonate reacting with sulphur dioxide

Answer 23

CaCO3(s) + 2H2O(l) + SO2(g) –> CaSO3(s) + 2H2O(l) + CO2(g)