Reaction of aqueous ions Flashcards
What is the colour of the solution when Cu2+ ions are hydrated to [Cu(H2O)6]2+
Blue solution
What is the colour of the solution when Fe2+ ions are hydrated to [Fe(H2O)6]2+
Pale green solution
What is the colour of the solution when Fe3+ ions are hydrated to [Fe(H2O)6]3+
Yellow brown solution (purple)
What is the colour of the solution when Al3+ ions are hydrated to [Al(H2O)6]3+
Colourless solution
Why are Fe3+ and Al3+ ions more acidic than Cu2+ and Fe2+?
Fe3+ is smaller and more highly charged than Fe2+
Fe3+ is more polarising
Fe3+ strongly attracts the lone pair on the oxygen of the water ligands
Weakens the O-H bond strength
Fe3+ complexes more easily release H+ ions making the solution acidic
Fe2+ ions do not release H+ ions
Write an equation to show Fe3+ complex act as an acid
[Fe(H2O)6]3+ → [Fe(H2O)5(OH)]2+ + H+
Reaction of [Fe(H2O)6]2+ with Na2CO3 equation
[Fe(H2O)6]2+ + CO32- —> FeCO3(s) + 6H2O
Observation of [Fe(H2O)6]2+ reacting with Na2CO3
Green precipitate
Observation of [Fe(H2O)6]2+ with NaOH
Green precipitate
(goes brown on standing in air as the oxygen oxidises Fe2+ to Fe3+)
Reaction of [Fe(H2O)6]2+ with NH3 equation
[Fe(H2O)6]2+ + 2NH3 → [Fe(H2O)4(OH)2] + 2NH4+
Observation of [Fe(H2O)6]2+ with NH3
Green precipitate
Brown on standing in air
Reaction of [Cu(H2O)6]2+ with Na2CO3 equation
[Cu(H2O)6]2+ + CO32- → CuCO3(s) + 6H2O
Observation of [Cu(H2O)6]2+ with Na2CO3
Blue-green precipitate
Observation of [Cu(H2O)6]2+ with NaOH
Blue precipitate
Reaction of [Cu(H2O)6]2+ with NH3 equation
[Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+
Observation of [Cu(H2O)6]2+ with NH3
Blue precipitate
Reaction of [Cu(H2O)6]2+ with excess NH3 equation
[Cu(H2O)6]2+ +4NH3 —> [Cu(H2O)2(NH3)4]2+ +4H2O
Observation of [Cu(H2O)6]2+ with excess NH3
Deep blue solution
Reaction of Cu(H2O)4(OH)2] with excess NH3 equation
Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+(aq) + 2H2O + 2OH-
Reaction of [Cu(H2O)6]2+ with chloride ions
[Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O
Observation of [Cu(H2O)6]2+ with chloride ions
Yellow solution
Reaction of [Fe(H2O)6]3+ with Na2CO3
2[Fe(H2O)6]3+ + 3CO32- → 2Fe(H2O)3(OH)3 + 3CO2 + 3H2O
Observation of [Fe(H2O)6]3+ with Na2CO3
Brown ppt and CO2 gas evolved which gives effervescence
Reaction of [Fe(H2O)6]3+ with NaOH
[Fe(H2O)6]3+ + 3OH- → Fe(H2O)3(OH)3 + 3H2O
Observation of [Fe(H2O)6]3+ with NaOH
Brown precipitate
Reaction of [Fe(H2O)6]3+ with NH3
[Fe(H2O)6]3+ + 3NH3 → Fe(H2O)3(OH)3 + 3NH4+
Observation of [Fe(H2O)6]3+ with NH3
Brown precipitate
Reaction of [Al(H2O)6]3+ with Na2CO3
2[Al(H2O)6]3+ + 3CO32- → 2Al(H2O)3(OH)3 + 3CO2 + 3H2O
Observation of [Al(H2O)6]3+ with Na2CO3
White precipitate and effervescence as CO2
gas evolved
Reaction of [Al(H2O)6]3+ with NaOH
[Al(H2O)6]3+ + 3OH- → [Al(H2O)3(OH)3] + 3H2O
Reaction of [Al(H2O)3(OH)3] with excess NaOH
[Al(H2O)3(OH)3] + OH- → [Al(H2O)2(OH)4]- + H2O
Observation of [Al(H2O)6]3+ with NaOH
White precipitate
Observation of [Al(H2O)3(OH)3] with excess NaOH
White precipitate dissolves to form a colourless solution
Reaction of [Al(H2O)6]3+ with NH3
[Al(H2O)6]3+ + 3NH3 → [Al(H2O)3(OH)3] + 3NH4+
Observation of [Al(H2O)6]3+ with NH3
White precipitate
How do Al3+ show amphoteric character?
Acting as a base (HCl added):
[Al(H2O)3(OH)3] + 3H+ → [Al(H2O)6]3+
Acting as an acid:
[Al(H2O)3(OH)3] + OH- → [Al(H2O)2(OH)4]- + H2O
