Group 2 Flashcards
Explain the trend in atomic radius (Mg-Ba)
-increases down group
-number of electrons increases
-more shells are needed
Explain the trend in first ionisation energy (Mg-Ba)
-decreases down group
-due to more shells
-increased shielding
-larger atomic radius
-weaker attraction between outermost electron and nucleus
Explain the trend in reactivity (Mg-Ba)
-increases down group
-increased shielding
-easier to lose electrons
explain the melting point of the elements in terms of their structure and bonding (Mg-Ba)
-decreases down group
-larger size of ions
-weaker attractive forces as it has to act over longer distance
The reactions of the elements Mg–Ba with water (and steam)
-redox reaction
-produces a metal hydroxide (alkaline solution) and hydrogen
-for example:
Mg(s) + 2H2O(l) → Mg (OH)2(aq) + H2(g)
Mg(s) + 2H2O(g) → MgO(s) + H2(g)
-when the metal oxides react with water, a group 2 hydroxide and hydrogen gas is formed
-the following ionic reaction takes place:
O2- (aq) + H2O (l) → 2OH- (aq)
X(OH)2 (aq) → X2+ (aq) + 2OH- (aq)
-going down the group, solubility of Group 2 hydroxides increases
-due to increase in concentration of OH- ions, hence increase in the pH of the solution (more alkaline)
-Group 2 metals react with steam to form metal oxide and hydrogen gas
The use of magnesium in the extraction of titanium from TiCl4
-titanium (IV) oxide is the main ore of titanium
-TiO2 is converted to titanium (IV) chloride (TiCl4) when heated in a chlorine gas with carbon.
-fractional distillation is used to purify the titanium chloride.
-the pure titanium chloride is then reduced by Mg in a furnace at a very high temperature (around 1000°C).
TiCl4 + 2Mg –> 2MgCl2 + Ti
The relative solubilities of the hydroxides of the elements Mg–Ba in water.
-going down the group, solubility of hydroxides increase
-means that solutions formed from reactions of group 2 metal oxides and water become more alkaline going down the group
is Mg(OH)2 soluble
sparingly soluble
uses of
Mg(OH)2/Ba in medicine
Ca(OH)2 in agriculture.
Uses of Calcium
-Ca(OH)2 neutralises acidic soils in agriculture
-due to calcium carbonate being largely insoluble, it acts more slowly than calcium hydroxide
Uses of Barium
-used in medicine as BaSO4
-barium meal/swallow containing BaSO4 is given to patient who needs an X-ray on their intestines
-barium absorbs X-rays so the gut shows up white on the image
-barium is toxic but is used in this form because
-barium sulfate is insoluble so is not absorbed into the blood
-barium meal or swallow is only a small amount for the patient to ingest
Uses of Magnesium
-Mg(OH)2 is partially soluble in water so safe to use
-used in suspension
-neutralises excess acid in the stomach and treat constipation
-Mg(OH)2 (s) + 2HCl (aq) → MgCl2 (aq) + 2H2O (l)
The use of CaO or CaCO3 to remove SO2 from flue gases.
-(SO2) is an air pollutant released from the burning of fossil fuels and contributes to acid rain and must be removed
-wet scrubbing is a process used to remove SO2 from flue gases
-flue gas = gas released from chimneys and exhausts of factories that burn fossil fuels
-powdered CaO or CaCO3 can both be used to remove SO2 from flue gases
-a slurry is made by combining CaO/CaCO3 and water
-slurry = thin and viscous fluid mixture which is sprayed onto the flue gases where the sulphur dioxide reacts with it to produce calcium sulfite (a solid waste product).
The relative solubilities of the sulfates of the elements Mg–Ba in water.
decreases going down the group
Is BaSo4 soluble or insoluble
what forms during the test for sulfate ions
-Insoluble
-formed as a white precipitate during the test for sulphate ions in solution
The use of acidified BaCl2 solution to test for sulfate ions.
explain why BaCl2 solution is used to test for sulfate ions and why it is acidified.
Ba2+(aq) + SO42-(aq) —> BaSO4(s)
BaCl2(aq) + MgSO4(aq) —>BaSO4(s) + MgCl2(aq)
-barium sulfate and barium carbonate are both insoluble
-sodium carbonate solution, would also give white precipitate if barium chloride solution added
The acid reacts with the carbonate ions to form carbon dioxide and water, and so gets rid of them before you add the barium chloride
You have to be careful about what acid you add to do this. For example, you can’t use dilute sulfuric acid, because that contains sulfate ions, and so will automatically give a white precipitate of barium sulfate.
If you are using barium chloride solution, you use hydrochloric acid. If you are using barium nitrate solution, you use nitric acid.
carbonate + dilute hydrochloric acid →
chloride + water + carbon dioxide
carbonate + dilute sulfuric acid →
sulfate + water + carbon dioxide
