Group 2 Flashcards
What is periodicity?
Repeating patterns/trends
All the group 2 metals react with water to produce a…
Metal hydroxide and hydrogen
Explain the reactivity of group 2 metals as you go down the group:
- The reactivity increases as you go down the group.
- The number of shells increases so the nuclear attraction between the outer electron and the nucleus decreases.
- This makes it easier to lose the electrons (act as reducing agents).
Explain how beryllium reacts with water:
State the observation:
No reaction with water
Explain the reactivity with water as you go down group 2:
Reactivity increases with water
Explain how Mg reacts with water, include equations both with steam and with warm water.
State the observation
Mg + H2O(g) -> MgO(s) + H2(g)
Mg + H2O (l) -> Mg(OH)2 (s) + H2(g)
There is no reaction with cold water.
Reacts with steam to form a white flame and a white powder of MgO
Reacts with warm water to form a white solid of Mg(OH)2
Explain how Ca reacts with water
State the observation
Ca(s) + 2H2O(l) -> Ca(OH)2(s) + H2(g)
Fizzes in water to form a white solid that is slightly soluble
Explain how Sr reacts with water:
State the observation
Sr + 2H2O(l) -> Sr(OH)2 (aq) + H2(g)
Bubbles and fizzing to form a colourless solution
Explain how Ba reacts with water:
State the observation
Ba + 2H2O(l) -> Ba(OH)2 (aq) + H2(g)
Bubbles and fizzing to form a colourless solution.
The solubility of group 2 hydroxides ….. as you go down the group
INCREASES
The solubility of group 2 sulphates …. as you go down the group
DECREASES
How can you test for sulphate ions?
- Add a small volume of hydrochloric acid to the sample
- Add barium chloride to the solution
- Record your results, if a white precipitate forms, sulfate ions are present.
Why is hydrochloric acid added before the barium chloride solution when testing for sulphate ions?
If there are carbonate ions present in the solution, insoluble white BaCO3 will form, which is the same result as if sulphate ions were present. Therefore, the HCL will react with the carbonate ions to form CO2 and H2O, preventing a false positive.
Sulphuric acid is not used as it contains sulfate ions that could react with the barium ions and provide a false positive.
How is BaSO4 used in medicine?
It is used as an imaging/contrast agent.
- Before a patient is sent for an X-Ray, they swallow a drink containing barium sulphate.
- The barium sulphate shows a strong contrast on the X-Ray allowing doctors to study the patient’s digestive system
Barium ions are super toxic to humans, why is it still safe to give a patient barium sulphate ions?
Barium sulphate is highly insoluble so it just passes straight through!
It won’t disassociate into ions
How is Mg(OH)2 used in medicine?
- It’s used to treat indigestion (e.g. heartburn, acid reflux)
- Indigestion is caused by stomach acid travelling up your oesophagus
- Therefore, as it is basic, it neutralises the stomach acid
How is Ca(OH)2 used in agriculture?
- Soil used for growing crops have an optimum pH
- If the soil is too acidic, it is treated with Slaked Lime Ca(OH)2
- It’s a base therefore neutralises the acid and raises the pH of the soil
How can we extract titanium using Magnesium?
- Titanium is a low density, strong and corrosion resistant metal.
- Reduction of the ore (TiO2) with C forms TiC, which is brittle
- Extraction by electrolysis does not make it pure enough
- Mg is used to form pure Titanium
What are the 2 equations for the extraction of titanium using magnesium?
1) TiO2 + 2Cl2 + 2C –> TiCl4 + 2CO
2) TiCl4 + 2Mg –> Ti + MgCl2
Why is this method of Titanium extraction expensive?
- High temperatures (high energy)
- TiCl4 purified by fractional distillation in inert argon atmosphere
- Cost of Mg (made by electrolysis)
What do we use flue gas desulfurisation for?
Can be used to remove SO2 from waste gases from furnaces such as coal fired power stations.
How does Flue Gas Desulphurisation work?
- The SO2 can be removed with an alkali in a process known as wet scrubbing
- Calcium oxide (Lima CaO) or calcium carbonate (lime CaCO3) are used.
- This chemical is sprayed along with water onto the flue gases.
- The gases pass through the wet scrubber containing basic calcium oxide so a neutralisation reaction can occur.
Which equations can take place in flue gas desulphurisation?
CaO + SO2 –> CaSO3
CaCO3 + SO2 –> CaSO3 + CO2
