Here are my revision notes for the Aqueous Ions section of the course.
Feel free to check out my other computer typed notes for parts of the 2nd year course on here.
I also have hand written notes of matching quality for pretty much the rest of the course (1st and 2nd year) if you're interested...
1.1. Reactions of Inorganic Compounds in Aqueous Solutions 1.2. Difference between Fe2+ and Fe3+ acidity
Dissolving Iron Nitrate in water Fe3+ is more acidic than Fe2+
Water molecules cluster around the iron so in aqueous Because: Fe3+ has a higher charge, so there is a higher
solutions it actually exists as [Fe(H20)6]2+ charge density than Fe2+, making it more strongly
polarising
The water molecules act as ligands forming 6 co-ordinate This means it draws electrons from the oxygen
bonds = octahedral which is co-ordinately bonded to it
This weakens the OH bonds
The same happens with an Iron (III) salt, except the complex is [Fe(H20)6]3+ Causing H+ ions to be more readily lost in the
solution
These are called aqua ions Decreasing the pH, making Fe3+ more acidic
**Rule – M3+ are generally more acidic than M2+
1.6. Distinguishing Iron Ions
1.3. Theories of Acidity Hydrolysis Reaction – using water molecules to break compounds
down (the water molecule is likely to break too)
Fe2+ and Fe3+ exist in aqueous solutions as octa
Lavoisier (1777) – said all acids contained oxygen, HCl disproved theory [Fe(H2O)6]2+ is pale green
Davy (1816) – said all acids contained hydrogen, doesn’t explain why [Fe(H20)6]3+ is pale brown when dilute,
hydrogen is important
Liebig (1838) – defined acids as substances containing hydrogen which Test – add dilute alkali, precipitates hydroxides w
could be replaced by a metal Inorganic Chemistry:
Fe3+ + 3OH- get → Fe(H2O)3(O
Arrhenius (1887) – acids produced H+ ions Reactions of Aqueous Ions
Fe2+ + 2OH- get → Fe(H2O)4(O
Bronsted Lowry – defined as substance that can donate a proton, base can 1.5. Reactions with CO3
accept a proton, difficulty with acids that do not contain
hydrogen (AlCl3) Iron (III) Carbonate doesn’t exist but Iron (II) Carbonate does
Lewis Theory – acids are electron pair acceptors and bases as electron pair Due to greater acidity of Fe3+
donors Carbonate can remove protons from [Fe(H2O)6]3+
but can’t remove them from the Fe2+ complex
1.4. Acid-Base Reactions of M2+ and M3+ ions
2[Fe(H2O)6]3+ +3CO32- → 2[Fe(H2O)3(OH)3] + 3CO2 + 3H2O 1.7. Amphoteric Hydroxides
[Fe(H2O)6]2+ + CO32- → FeCO3 + 6H2O Amphoteric – showing both acidic and basic p
**Rule – Carbonates of M2+ exist, while M3+ carbonates do not Aluminium Hydroxide is example, reacts with
Al(H2O)3(OH)3 + 3HCl → A
Reacts with acid, therefore
The neutral metal hydroxide formed is essentially M(OH)3, it’s
Ammonia has the same effect as hydroxide ions in Al(H2O)3(OH)3 + OH- → [Al
uncharged, insoluble and forms a ppt
removing protons – both basic
The neutral metal hydroxide formed is essentially M(OH)2, it’s
uncharged, insoluble and forms a ppt
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