Chemistry 3.2.2

Question 1

What is an acid and a base?

Answer 1

Acids are proton donors (H+) and bases are proton acceptors and electron pair donors.

Question 2

What happens when group 2 metals react with water?

Answer 2

The metal loses electrons and becomes a 2+ metal ion. Reactions are more vigorous so there are more successful collisions within a given time.

Question 3

what is the trend in reactivity of group 2 metals down the group?

Answer 3

Reactivity increases as atoms become larger and the distance between the nucleus and outer electrons is greater.

Question 4

What are the solubilities of group 2 metal hydroxides?

Answer 4

Mg(OH)2(s) (vary sparingly soluble, pH 8-9). Ca(OH)2(s) (sparingly soluble, pH 10-11). Sr(OH)2(aq) (slightly soluble pH 11-12). Ba(OH)2(aq) (soluble 12-13).

Question 5

What is the trend in solubility of group 2 metal hydroxides?

Answer 5

Solubility increases. The strength of the hydroxides as a base increases down a group as there are more hydroxide ions in the solution.

Question 6

Why is beryllium not included in the majority of this section?

Answer 6

Be is very small and highly charged, so polarising. this gives it and its compounds anomalous properties.

Question 7

What is the test for hydroxide ions?

Answer 7

Adding MgCl to a solution containing hydroxide ions forms a white ppt of Mg(OH)2.
MgCl2 + 2NaOH → Mg(OH)2 (white ppt) + 2NaCl
Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s) (ionic equation).

Question 8

What is the test for magnesium ions?

Answer 8

Adding sodium hydroxide to a solution containing magnesium ions forms a white ppt of Mg(OH)2.
MgCl2 + 2NaOH → Mg(OH)2 (white ppt) + 2NaCl
Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s) (ionic equation).

Question 9

What happens when sodium hydroxide is added to badium chloride?

Answer 9

No visible change as BaCl2 is soluble in water.

Question 10

What are the solubilities of group 2 sulphates?

Answer 10

MgSO4(aq) (soluble). CaSO4(s) (slightly soluble). SrSO4(s) (sparingly soluble). BaSO4(s) (insoluble).

Question 11

What is the trend in solubility of group 2 sulphates?

Answer 11

Decreases down the group.

Question 12

What is the test for sulphate ions?

Answer 12

Adding barium sulphate (insoluble) to water forms a white ppt.
Ba2+(aq) + SO4(aq) → BaSO4(s) (ionic equation)
BaCl2 + 2NaSO4 → BaSO4 (white ppt) + 2NaCl.

Question 13

What happens when MgCl2 is added to NaSO4?

Answer 13

No ppt is formed as MgSO4 is soluble in water.
MgCl2 + Na2SO4 → MgSO4
2NaCl.

Question 14

What are the products of reacting group 2 hydroxides with acids?

Answer 14

Salt and water (Be(OH)2 is the exception because it’s amphoteric).
Mg(OH)2 + HCl → MgCl2 + H2O
Ca(OH)2 + H2SO4 → CaSO4 + H2O.

Question 15

When testing for barium ions what must be done?

Answer 15

The unknown solution must be acidified with HCl or HNO3 to remove carbonate ions that would interfere with the reaction.

Question 16

Why can’t H2SO4 be used to acidify BaCl2?

Answer 16

It contains sulphate ions which would form a white ppt of BaSO4.

Question 17

What is the test for barium ions?

Answer 17

Adding H2SO4 to a solution containing barium ions forms a white ppt of BaSO4.

Question 18

What is a use of Mg(OH)2?

Answer 18

Treat indigestion as it neutralises excess stomach acid.

Question 19

What is a use of Ca(OH)2?

Answer 19

Neutralising soil.

Question 20

What is a use of BaSO4?

Answer 20

Barium meal. When ingested it coats the stomach, oesophagus and intestines so that they appear on x-rays.

Question 21

Why is BaSO4 used even though its toxic?

Answer 21

It’s insoluble so it safe to use.

Question 22

How is titanium extracted?

Answer 22

Reducing titanium chloride with a more reactive metal. Mg is used as a reducing agent, and is heated with the titanium chloride in a crucible in an atmosphere of argon (condition), to prevent oxidation, at 600 degrees (condition-high temp):
TiCl4(g) + 2Mg(l) → Ti(s) + 2MgCl2(l)

Question 23

What is done to a titanium odide ore before the product is reduced?

Answer 23

Titanium oxide in an ore of rutile (TiO2) is converted into titanium chloride using chlorine and coke at around 900 degrees (condition-high temp).
TiO2(s) + 2Cl2(g) + 2C(s) → TiCl4(g) + 2CO(g).

Question 24

What is flue gas desulphurization and how is SO2 removed?

Answer 24

Removes SO2 from the gases emitted by fossil fuel plants and other SO2 emitting processes. SO2 is removed by using CaO or CaCO4 to neutralise the SO2(g)
CaO(s) + SO2(g) → CaSO3(s).

Question 25

Why is desulfurization important?

Answer 25

It prevents the release of SO2 into the atmosphere which would cause acid rain.