inorganic chemrevise Flashcards
Reactivity of group 2 metals
increases down the group
Group 2 reactions
Reactions with oxygen.
burn in oxygen
Mg burns with a bright white flame
MgO appears as a white powder.
2 Mg + O2 2 MgO
Group 2 reactions with water
reacts in steam to produce magnesium oxide and hydrogen
bright white flame
MgO appears as a white powder.
Mg(s) + H2O(g) MgO(s) + H2(g)
Mg will also react with warm water
Mg + 2 H2OMg(OH)2 + H2
This is a much slower reaction than the reaction with steam and there is no flame.
group 2 metals will react with cold water
increasing vigour down the group to form hydroxides.
fizzing
metal dissolving
calcium a white precipitate
Steps in extracting titanium
- 2.
3.
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
TiCl4 + 2Mg Ti + 2 MgCl2
Why titanium is expensive
expensive cost of the magnesium
High temperatures required in both steps
whats used to remove so2
Calcium oxide
flue gas desulfurisation
containing basic calcium oxide which reacts with the acidic sulfur dioxide in a neutralisation reaction.
SO2 + CaOCaSO3
Magnesium hydroxide
insoluble in water
Mg2+(aq) + 2OH-(aq)Mg(OH)2(s).
eutralise excess acid in the stomach and to treat constipation.
Calcium hydroxide
white precipitate It is used in agriculture to neutralise acidic soils.
e limewater turns cloudy as white calcium carbonate is produced.
Ca(OH)2 (aq) + CO2 (g) CaCO3 (s) + H2O(l)
Solubility of sulfates
Group II sulfates become less soluble down the group. BaSO4 is the least soluble.
Testing for presence of a sulfate ion
BaCl2 solution acidified with hydrochloric acid is used as a reagent to
test for sulfate ions.
Ba2+ (aq) + SO42-(aq)BaSO4 (s).
potassium chlroide with
chlrine
bromine
iodine
Very pale green solution, no reaction
Yellow solution, no reaction
Brown solution, no reaction
potassium bromide (aq) with clorine
bromine
iodine
Yellow solution, Cl has displaced Br
Yellow solution, no reaction
Brown solution, no reaction
potassium iodide (aq)
Brown solution, Cl has displaced I
Brown Solution, Br has displaced I
Brown Solution, no reaction
The reactions of halide ions with silver nitrate
Fluorides produce no precipitate
Chlorides produce a white precipitate Ag+(aq) + Cl- (aq) AgCl(s)
Bromides produce a cream precipitate Ag+(aq) + Br- (aq)AgBr(s)
Iodides produce a pale yellow precipitate Ag+(aq) + I- (aq) AgI(s)
Silver chloride in dilute ammonia
AgCl(s) + 2NH3(aq) [Ag(NH3)2]+ (aq) + Cl- (aq)
Colourless solution
silver bromide conc ammonia
to form a
complex ion
AgBr(s) + 2NH3(aq) [Ag(NH3)2]+ (aq) + Br - (aq)
Colourless solution
iodine and sulfer
White steamy fumes of HI are evolved. Black solid and purple fumes of Iodine are also evolved
A colourless, acidic gas SO2
A yellow solid of sulfur
H2S (Hydrogen sulfide), a gas with a bad egg smell,
Disproportionation
element simultaneously oxidises and reduces.
chlrone and water
Cl (g) + HO(l)⇌ HClO(aq) + HCl(aq)
chlroine and diulte naoh
Cl2,(and Br2, I2) in aqueous solutions will react with cold sodium hydroxide. The colour of the halogen solution will fade to colourless.
Cl2 (aq) + 2 NaOH (aq) NaCl (aq) + NaClO (aq) + H2O (l)
The mixture of NaCl and NaClO is used as bleach and to disinfect/ kill bacteria.
soodumand cold water
It fizzes around on surface etc. 2Na(s)+2H2O(l)2NaOH(aq)+H2 (g)
mag and cold water
Magnesium reacts very slowly with cold water to form the hydroxide but reacts more readily with steam to form the oxide Mg (s) + H2O (g)MgO (s) + H2 (g)
period 3 flame colours
Sodium burns with a yellow flame to produce a white solid.
Mg, Al, Si and P burn with a white flame to give white solid smoke.
S burns with a blue flame
ipnic oxide
The metal oxides (Na2O, MgO, Al2O3) are ionic. They have high melting points. They have ionic giant lattice structures: strong forces of attraction between oppositely charged ions : higher mp. They are ionic because of the large electronegativity difference between metal and O
The increased charge on the cation makes the ionic forces stronger (bigger lattice enthalpies of dissociation) going from Na to Al so leading to increasing melting points.
Al2O3 is ionic but does show some covalent character. This can be explained by the electronegativity difference being less big or alternatively by the small aluminium ion with a high charge being able to get close to the oxide ion and distorting the oxide charge cloud.
macromoelcue oxides
SiO2 is macromolecular: It has many very strong covalent bonds between atoms. High energy needed to break the many strong covalent bonds – very high mp +b
simple molecular oxides
P4O10 (s), SO2 (g) are simple molecular with
weak intermolecular forces between molecules (van der waals + permanent dipoles) so have lower mp’s. They are covalent because of the small electronegativity difference between the non-metal and O atoms. P4O10 is a molecule containing 4P’s and 10 O’s. As it is a bigger molecule and has more electrons than SO2 it will have larger van der waals forces between molecules and a higher melting point.
Metal ionic oxides tend to react with water
form hydroxides which are alkaline
Na2O (s) + H2O (l)2Na+ (aq) + 2OH- (aq) pH 13 (This is a vigorous exothermic reaction)
The ionic oxides are basic because the oxide ions accept protons to become hydroxide ions in this reaction (acting as a Bronsted-Lowry base)
MgO (s) + H2O (l)Mg(OH)2 (s) pH 9
Mg(OH)2 is only slightly soluble in water as its lattice is stronger sofewerfreeOH- ionsareproducedandsolowerpH.
non-metal, simple molecular, covalent, oxides react with water to give
acids. P4O10 (s) + 6 H2O (l) 4 H3PO4(aq) pH 0 (this is a vigorous exothermic reaction) SO2 (g) + H2O (l) H2SO3 (aq) pH 3 (weak acid) SO2 + H2O H+ + HSO3- SO3 (g) + H2O (l) H2SO4 (aq) pH 0 SO3 + H2O H+ + HSO4
Reactions of halides with silver nitrate
Fluorides produce no precipitate Chlorides produce a white precipitate Ag+(aq) + Cl- (aq) AgCl(s) Bromides produce a cream precipitate Ag+(aq) + Br- (aq)AgBr(s)
Iodides produce a pale yellow precipitate Ag+(aq) + I- (aq) AgI(s)
