1 - Inorganic Chemistry Flashcards
Group 2 Reactions
With water:
-X + 2H2O —> X(OH)2 + H2
-Redox reaction (metal is oxidised, hydrogen is reduced)
-Forms metal hydroxide and hydrogen gas
-Magnesium only reacts vigorously with steam (not water)
With Oxygen:
-Forms metal oxide
-Combustion reaction
-Redox (metal is oxidised, oxygen is reduced)
With dilute acid:
-Forms salt and hydrogen
-Redox (metal is oxidised, hydrogen is reduced)
Group 7 Reactivity and Displacement Reactions:
More reactive element displaces less reactive element
Displaced element is oxidised, displacer is reduced
Chlorine
-pale green solution when present
Bromine
- yellow solution when present
Iodine
-brown (without organic solvent)
-purple (with organic solvent)
observation of reaction of magnesium with steam
Bright white light
White powder
Group 7 trends
BP increases down the group as more electrons so more van der waals forces
IN decreases down group
Atomic radius increases down group
insoluble compounds
All carbonates
Most hydroxides (alkali metals are soluble)
(Except potassium, sodium, ammonium)
soluble compounds
potassium compounds
ammonium compounds
sodium compounds
Most sulfates (lead, barium, calcium)
Most chlorides (lead, silver)
Chlorine Disproportionation Reactions
one mole of chlorine, 2 moles of sodium hydroxide:
products - NaCl + NaClO + H2O
one mole of chlorine and one mole of water:
products -HCl +HClO
common acid formulas (proton donor)
HCl Hydrochloric acid
H2SO4 sulphuric acid
HNO3 nitric acid
H3PO4 phosphoric acid
common base formulas (proton acceptors)
NaOH sodium hydroxide
KOH potassium hydroxide
NH3 ammonium
Halogens Redox Reaction
Halogens are oxidising agents
Oxidising ability of halogens decreases down the group
Halide ions are reducing agents
Reducing ability of halide ions increases down the group
Group 2 Sulphates and Hydroxides
Hydroxides: Solubility increases down group
Sulphates: Solubility decreases down group
halide ions test
-dilute nitric acid
-silver nitrate solution
-chloride: white
bromide: cream
iodide: yellow
-hard to distinguish between colours so ammonia solution can be added
–chloride dissolves in dilute ammonia
solution
bromide will only dissolve in
concentrated ammonia solution
iodide will not dissolve in dilute or
concentrated ammonia solution (it is
insoluble)
Period 3 trends
Melting Points
-Na-Al: Metallic bonding so high
-Si : Highest because giant molecular structure and covalent bonds
-P-Ar: Simple molecular structure (S is higher because larger molecule)
Ionisation Energy:
-Increases except aluminium (3p) and sulfur (electron pair)
Atomic Radius
-Decrease
Group 2 Uses
Magnesium oxide - neutralise excess stomach acid, safe to use because only partially soluble so solution is only partially alkaline
Calcium carbonate, oxide, hydroxide - raise pH of soil
Barium Sulphate: Medicine, X-ray on intestines, absorbs X-ray and barium is usually toxic but since barium sulphate is insoluble, won’t be absorbed by blood
Group 7 Reactions
When reacting with metals, strong oxidising agents
Oxidising ability decreases down group
Sodium Halides and Concentrated Sulfuric Acid
H2SO4(l) + X-(aq) → HX(g) + HSO4-(aq)
1) Sodium Chloride and Sodium Fluoride
-Weak reducing agents so no redox reaction
-Steamy white fumes observed (HCL or HF)
2) Sodium Bromide
-After initial acid-base reaction, sulfur is reduced and bromine is oxidised
-Steamy white fumes (HBr), Orange/Brown fumes (Br), colourless acidic gas (SO2)
-Reduction product: sulfur dioxide
3) Sodium Iodide
-After initial reaction, sulfur reduced to sulfur dioxide, then to sulfur, then to hydrogen sulfide
-Steamy white fumes (HI), black solid and purple fumes(I), colourless acidic gas (SO2), yellow solid (S), gas with rotten egg smell (hydrogen sulfide)
Group 2 Trends
IE decrease
BP decrease
Reactivity increase
Flue gas desulfurisation
calcium oxide used to remove sulfur dioxide and other waste gases from furnaces
gases pass through a scrubber containing basic calcium oxide which
reacts with the acidic sulfur dioxide in a neutralisation reaction
SO2 + CaO –> CaSO3
why silver nitrate solution acidified with nitric acid
so no carbonate ions interfere
cannot be HCL because chloride ions in HCL will interfere and form white ppt
