INORGANIC - GROUP 2 Flashcards
describe the trend in atomic radius
atomic radius increases down the group
this is because the atoms have more shells of electrons making the atom bigger
describe the trend in melting points
Decreases
weaker metallic bonding as the atomic size increases - the distance between the positive ions and delocalised electrons also increases
Therefore the electrostatic forces between the positive ions and delocalised electrons weakens
- magnesium is an exception from this rule as its crystals can’t pack as closely together
Trend in 1st ionisation energy
DECREASES
outermost electrons are held more weakly as they are successively further from the nucleus
the outer shell electrons are more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons
magnesium and steam reaction
reacts to produce magnesium oxide and hydrogen
Mg would burn with a bright white flame - MgO appears as a white powder
Mg + H2O —> MgO + H2
magnesium and water reaction
produces magnesium hydroxide
slower reaction than steam as there is no flame
Mg + 2H2O —-> Mg(OH)2 + H2
Other reaction with water
react to form hydroxides
Ca + 2H2O —> Ca(OH)2 + H2
Sr + 2H2O —> Sr(OH)2 + H2
Ba + 2H2O —> Ba(OH)2 + H2
observations with water
fizzing, (more vigorous down group)
the metal dissolving, (faster down group)
the solution heating up (more down group)
with calcium a white precipitate appearing
(less precipitate forms down group with
other metals)
What is titanium used for
making strong, light alloys for use in airfact
Why is magnesium used to extract titanium
as it is more reactive metal than titanium
- titanium cannot be extracted with carbon as TIC is formed
- no electrolysis has it has to be very pure
Steps in extracting titanium
- TiO2 (solid) is converted to TiCl4
(liquid) at 900C: - The TiCl4 is purified by fractional distillation in an argon
atmosphere. - The Ti is extracted by Mg in an argon atmosphere at 500C
Why is titanium extraction expensive
- Mg is expensive
- Batch process expensive as process is slower
- High temps required
Mg and Ti equation
TiO2 + 2 Cl2 + 2 C —–> TiCl4 + 2 CO
TiCl4 + 2Mg —-> Ti + 2 MgCl2
Trend in solubility of hydroxides
more soluble down the group
if its insoluble then white precipitates will be formed
Magnesium hydroxide solubility
classed as insoluble in water
simplest ionic equation =
– Mg2+(aq) + 2OH-(aq) —> Mg(OH)2 (s).
magnesium hydroxide in water will
appear slightly alkaline (pH 9) so some hydroxide ions must therefore have been produced by a very slight dissolving and therefore it can be classed as sparingly soluble
How is magnesium hydroxide used in medicine
to neutralise excess acid in the stomach and to treat constipation
- Mg(OH)2 + 2HCl —-> MgCl2 + 2H2O
it is so weakly alkaline. It is
preferable to using calcium carbonate as it will not
produce carbon dioxide gas.
Calcium hydroxide solubility
Classed as partially soluble in water and will appear as a white precipitate
Used in agriculture to neturalise acidic soils
Aqueous solution of CaOH is called lime water and can be used to test for CO2
Ca(OH)2 (aq) + CO2 (g) —> CaCO3 (s) + H2O(l)
Barium hydroxide solubility
Easily dissolve in water
Hydroxide ions present make the solution strongly alkaline
Ba(OH)2(s) + aq —> Ba2+ (aq) + 2OH-(aq)
What is the least soluble sulfate
BaSO4
BaSO4 use in medicine
used as a barium metal and is given to patients who need x-rays of their intestine
barium absorbs the x-ray and so the gut shows up on the x-ray image
testing for presence of a sulfate ion
BaCl2 solution acidified with hydrochloric acid is used as a reagent to test for sulfate ions
The hydrochloric acid is needed to react with carbonate impurities that are often found in salts which
would form a white barium carbonate precipitate and so give a false result. You could not use sulfuric acid
because it contains sulfate ions and so would give a false positive result
If acidified barium chloride is added to a solution that contains sulfate ions a
white precipitate of barium
