Chemistry 3.2.2 Flashcards
What is an acid and a base?
Acids are proton donors (H+) and bases are proton acceptors and electron pair donors.
What happens when group 2 metals react with water?
The metal loses electrons and becomes a 2+ metal ion. Reactions are more vigorous so there are more successful collisions within a given time.
what is the trend in reactivity of group 2 metals down the group?
Reactivity increases as atoms become larger and the distance between the nucleus and outer electrons is greater.
What are the solubilities of group 2 metal hydroxides?
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).
What is the trend in solubility of group 2 metal hydroxides?
Solubility increases. The strength of the hydroxides as a base increases down a group as there are more hydroxide ions in the solution.
Why is beryllium not included in the majority of this section?
Be is very small and highly charged, so polarising. this gives it and its compounds anomalous properties.
What is the test for hydroxide ions?
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).
What is the test for magnesium ions?
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).
What happens when sodium hydroxide is added to badium chloride?
No visible change as BaCl2 is soluble in water.
What are the solubilities of group 2 sulphates?
MgSO4(aq) (soluble). CaSO4(s) (slightly soluble). SrSO4(s) (sparingly soluble). BaSO4(s) (insoluble).
What is the trend in solubility of group 2 sulphates?
Decreases down the group.
What is the test for sulphate ions?
Adding barium sulphate (insoluble) to water forms a white ppt.
Ba2+(aq) + SO4(aq) → BaSO4(s) (ionic equation)
BaCl2 + 2NaSO4 → BaSO4 (white ppt) + 2NaCl.
What happens when MgCl2 is added to NaSO4?
No ppt is formed as MgSO4 is soluble in water.
MgCl2 + Na2SO4 → MgSO4
2NaCl.
What are the products of reacting group 2 hydroxides with acids?
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.
When testing for barium ions what must be done?
The unknown solution must be acidified with HCl or HNO3 to remove carbonate ions that would interfere with the reaction.
Why can’t H2SO4 be used to acidify BaCl2?
It contains sulphate ions which would form a white ppt of BaSO4.
What is the test for barium ions?
Adding H2SO4 to a solution containing barium ions forms a white ppt of BaSO4.
What is a use of Mg(OH)2?
Treat indigestion as it neutralises excess stomach acid.
What is a use of Ca(OH)2?
Neutralising soil.
What is a use of BaSO4?
Barium meal. When ingested it coats the stomach, oesophagus and intestines so that they appear on x-rays.
Why is BaSO4 used even though its toxic?
It’s insoluble so it safe to use.
How is titanium extracted?
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)
What is done to a titanium odide ore before the product is reduced?
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).
What is flue gas desulphurization and how is SO2 removed?
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).
Why is desulfurization important?
It prevents the release of SO2 into the atmosphere which would cause acid rain.
