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.
What does MgO look like at room temperature?
A white powder
Which Group 2 metal compound looks like a white powder at room temperature?
MgO
What are the observations when Mg and O2 reacts?
Bright white light
What are the observations when Ca and O2 reacts?
Red flame
Which Group 2 metal reacts with O2 to give off a bright white light?
Mg
Which Group 2 metal reacts with O2 to give off a red flame?
Ca
What are the observations when Sr and O2 reacts?
Orange-red flame
Which Group 2 metal reacts with O2 to give off a orange-red flame?
Sr
What are the observations when Ba and O2 reacts?
Green flame
Which Group 2 metal reacts with O2 to give off a green flame?
Ba
What are the products when Ba and H2O react?
BaO2 as well as BaO
Which reaction produces both BaO2 and BaO?
Reaction between BaO and H2O
What’s an observation during any reaction where H2 is formed?
Bubbles
If bubbles are produced during a reaction, that’s a big indication that which substance is being formed?
H2
Give a reagent (or combination of reagents) that, when
added separately to butan−2−ol and 2−methylpropan−2−ol, could be used to distinguish between them.
State what is observed
- Acidified Potassium Dichromate / K2Cr2O7/H+
- Butano-2-ol has observation of green solution
- 2-methylpropan-2-ol has no observed change so solution remains orange
Give a reagent (or combination of reagents) that, when
added separately to aqueous silver nitrate and aqueous sodium nitrate, could be used to distinguish between them.
State what is observed in each case
- Any soluble chloride including hydrochloric acid (ignore concentration)
- White precipitate or white solid / white suspension
- Remains colourless / no reaction / no (observed) change / no
precipitate / clear solution / it remains clear
OR as an alternative
- Any soluble iodide including HI
- Yellow precipitate or yellow solid / yellow suspension
- Remains colourless or no reaction or no (observed) change or no
precipitate or clear solution or it remains clear
OR as an alternative
- Any soluble bromide including HBr
- Cream precipitate or cream solid / cream suspension
- Remains colourless or no reaction or no (observed) change or no
precipitate or clear solution or it remains clear
OR as an alternative
- NaOH or KOH or any soluble carbonate
- Brown precipitate or brown solid / brown suspension with NaOH / KOH
(white precipitate / solid / suspension with carbonate) - Remains colourless or no reaction or no (observed) change or no
precipitate or clear solution or it remains clear
Ignore “cloudy solution” OR “suspension”
Ignore “nothing (happens)”
Ignore “no observation”
Ignore “clear” on its own
Ignore “dissolves”
Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water. Also, state the role of water in this reaction
- Ca (s) + 2H2O (l) -> Ca^2+ (aq) + 2OH– (aq) + H2 (g)
- Oxidising Agent
You are given a sample of saturated calcium hydroxide solution. Outline the practical steps that you would take to determine the solubility of calcium hydroxide in this solution
Take a known volume of the saturated solution. Evaporate the filtrate to dryness
Allow titrate with dilute HCl or HNO3
Weigh the residue of known / specified concentration
Ignore any references to indicators
A student added barium chloride solution to sodium sulfate solution. The student filtered off the precipitate and collected the filtrate. Give an ionic equation for the formation of the precipitate
Ba^2+ (aq) + SO4^2- (aq) -> BaSO4 (s)
We should know that this is equation and not the one that forms NaCl because we should know that BaSO4 is highly insoluble so would be a precipitate in solution
