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