Group 2 Flashcards
Which one of the following is a correct procedure for isolating a sample of hydrated copper(II) sulphate
from a mixture of hydrated copper(II) sulphate and barium sulphate?
- filter, crystallise filtrate, dry the crystals
- add water, filter, crystallise filtrate, dry the crystals
- filter, dry the solid on the filter paper
- add water, filter, dry the solid left on the filter paper
add water, filter, crystallise filtrate, dry the crystals
Which one of the following solutions would not give a white precipitate when added to barium
chloride solution?
- silver nitrate solution
- dilute sulphuric acid
- sodium nitrate solution
- sodium sulphate solution
sodium nitrate solution
An aqueous solution of a sodium salt gave no precipitate when treated with either silver nitrate solution or barium chloride solution. Which one of the following could be the formula of the
sodium salt?
- NaF
- NaI
- Na2SO4
- NaBr
NaF
Which group is more reactive - 1 or 2?
1
What’s the general rule for the trend of solubility of a metal compound?
As a general rule:
- If the anion has a -2 charge (such as SO4^2-), the compound becomes less soluble going down the group
- If the anion has a -1 charge (such as OH-), the compound becomes more soluble going down the group
What’s the trend in solubility of group 2 hydroxides going down the group?
Increasing
What’s the trend in solubility of group 2 sulphates going down the group?
Decreasing
State some uses of Group 2 metal compounds (3)
- Sulphate Test
- Neutralisation
- Barium Meal
- Titanium Extraction
- Removal of SO2
Describe and explain the use of a Group 2 metal compound in the Sulphate test
We can use Barium Chloride (BaCl2) to test if a solution contains sulphate ions by:
- Adding hydrochloric acid (HCl) to remove any carbonates in the solution, as these will produce a white precipitate after addition of BaCl2, which will be a false positive.
- Adding BaCl2 to precipitate BaSO4 out of solution as it is highly insoluble following the full and ionic equations:
Ba^2+ (aq) + SO4^2- (aq) -> BaSO4 (s)
Describe and explain the use of a Group 2 metal compound in Neutralisation
- Alkaline group 2 compounds can be used to neutralise acids.
- For example, Calcium hydroxide (Ca(OH)2), also known as ‘slaked lime’, is used to neutralise acidic soils.
- Whereas Magnesium hydroxide (Mg(OH)2), or magnesia milk, is used as an antacid to neutralise excess stomach acid.
- The ionic equation for these reactions would be:
H+ (aq) + OH- (aq) -> H2O (l)
Describe and explain the use of a Group 2 metal compound in the Barium Meal
The insoluble Barium Sulphate (BaSO4) can be used in a medical procedure. A patient who needs an X-ray of soft tissues such as the stomach will be given a BaSO4 suspension to be ingested. This compound will coat the stomach linings and when exposed to X-ray will absorb the rays, exposing the soft tissues on a radiograph. An x-ray will normally just pass through soft tissues, so this is useful. Barium is a toxic metal, but BaSO4 is insoluble and will not be absorbed into the bloodstream to poison the body. In fact, the compound will eventually be naturally and safely secreted out via large intestines.
Describe and explain the use of a Group 2 metal compound in the Titanium Extraction and why this process is important
- Titanium is a light but strong metal that is resistant to corrosion and high temperatures; it is used in aeroplane structures.
- Magnesium can be used to extract titanium from its ore, titanium oxide (TiO 2) by:
1. Heating TiO2 with carbon and chlorine gas to produce titanium (IV) chloride (TiCl4)
2. Passing TiCl4 through fractional distillation column to purify
3. Reducing purified TiCl4 with Magnesium at 1000°C to titanium:
TiCl4 (g) + 2Mg (l) -> Ti (s) + 2MgCl2 (l)
Describe and explain the use of a Group 2 metal compound in the Removal of SO2
Burning fossil fuels like coal produce Sulphur Dioxide pollutant gas. A ‘wet scrubbing’ process involving an alkali can be used to neutralise Sulphur Dioxide in the flue gases. This is done by spraying Calcium Carbonate and Calcium Oxide (Ca2CO3 / CaO) solutions on the acidic Sulphur Dioxide gases coming out of chimney flues.
CaCO3 (s) + 2H2O (l) + SO2 (g) -> CaSO3 (s) + 2H2O(l) + CO2 (g)
CaO (s) + 2H2O (l) + SO2 (g) -> CaSO3 (s) + 2H2O (l)
The reaction of Ca2CO3 / CaO with SO2 produces Calcium Sulphite (CaSO3) that in turn can be used in the production of plasterboards.
What are flue gases?
Gases produced by power stations which are harmful to the environment
Describe and explain the trend in melting and boiling point down group 2
There is a general decreasing trend in the melting points of Group 2 elements going down the group. As we go down Group 2, we will see the following:
- Increase in atomic radius and size
- Number of delocalised electrons stay constant, 2 electrons
- Nuclear charge +2 remains the same
- So there is a weaker attractive force from the nucleus
- Making it easier to loosen the metallic bonds, requiring less energy
- Lowering the melting point.