2.6 Aqueous ions Flashcards
What is a Lewis acid?
An electron pair acceptor.
What is a Lewis base?
An electron pair donor.
In complex ions, which is the Lewis base and which is the Lewis acid?
Ligand is the Lewis base; metal ion is the Lewis acid.
What are examples of 2+ metal-aqua ions?
[Fe(H2O)6]2+ (green), [Cu(H2O)6]2+ (blue).
What are examples of 3+ metal-aqua ions?
[Al(H2O)6]3+ (colourless), [Fe(H2O)6]3+ (violet).
Why does Fe(III) appear yellow/brown in solution?
Due to hydrolysis reactions.
Which is more acidic: [M(H2O)6]3+ or [M(H2O)6]2+?
[M(H2O)6]3+, due to higher charge density and polarising power.
What effect does high polarising power have on water ligands?
It weakens O-H bonds, promoting H+ release.
What colour is the precipitate formed from Cu2+ with limited OH- or NH3?
Blue.
What precipitate forms with Fe2+ and limited OH-/NH3?
Green.
What precipitate forms with Fe3+ and limited OH-/NH3?
Brown.
What precipitate forms with Al3+ and limited OH-/NH3?
White.
What happens when Al(OH)3 dissolves in excess OH-?
Forms [Al(OH)4]−, a colourless solution.
Why is Al(OH)3 considered amphoteric?
It reacts with both acids and bases.
What complex forms with excess NH3 and Cu2+?
[Cu(NH3)4(H2O)2]2+, deep blue solution.
Does Cu2+ undergo complete ligand substitution with NH3?
No, substitution is incomplete.
What forms when 2+ ions react with carbonate?
Metal carbonate precipitates (e.g., CuCO3, FeCO3).
What forms when 3+ ions react with carbonate?
Hydroxide precipitate and CO2 gas.
Give an equation for Fe3+ reacting with carbonate.
2[Fe(H2O)6]3+ + 3CO3^2- → 2Fe(OH)3(H2O)3 + 3CO2 + 3H2O.
Give an equation for Cu2+ reacting with carbonate.
[Cu(H2O)6]2+ + CO3^2- → CuCO3 + 6H2O.
What complex forms when excess Cl- reacts with Cu2+?
[CuCl4]2−, a green solution.
What complex forms when excess Cl- reacts with Fe2+?
[FeCl4]2−, a yellow solution.
What does [Fe(H2O)6]2+ become in air or H2O2?
Fe(OH)3(H2O)3, brown ppt.
