Reactions of aqueous ions Flashcards
What is meant by enthalpy of hydration?
- standard enthalpy change
- when one mole of gaseous ions
- covered into one mole of aqueous ions
enthalpy of hydration is…
- always exothermic
- bonds made with water molecules
What is a co-ordinate bond?
- shared pair of electrons
- that have come from the same atom
What is a ligand?
- ion/molecule with lone pair of electrons
- forms co-ordinate bond with transition metal ion
What is a complex ion?
central atom/ion surrounded by ligands
What is the co-ordination number?
number of co-ordinate bonds formed by transition metal ion
What are the 4 hexa aqua ions?
[Fe(H2O)6] 2+
[Fe(H2O)6] 3+
[Cu(H2O)6] 2+
[Al(H2O)6] 3+
What colour solution does Cu 2+ give when hydrated?
[Cu(H2O)6] 2+ (aq)
Blue solution
What colour solution does Fe 2+ give when hydrated?
[Fe(H2O)6] 2+ (aq)
Pale green solution
What colour solution does Fe 3+ give when hydrated?
[Fe(H2O)6] 3+ (aq)
Purple solution
may look yellow/brown
What colour solution does Al 3+ give when hydrated?
[Al(H2O)6] 3+ (aq)
Colourless solution
Why are the 3+ ions more acidic?
- Fe3+ smaller and more highly charged than Fe2+
- so Fe3+ more polarising
- Fe3+ attracts LP on oxygen of water ligands more strongly
- weakens O-H bond strength
- Fe3+ complex more easily releases H+
- Fe2+ does not release H+
What is the equation which represents [Fe(H2O)6] 3+ acting as an acid?
[Fe(H2O)6] 3+ —> [Fe(H2O)5(OH)] 2+ + H+
OR
[Fe(H2O)6] 3+ + H2O —> [Fe(H2O)5(OH)] 2+ + H3O+
What is the equation which represents [Al(H2O)6] 3+ acting as an acid?
[Al(H2O)6] 3+ —> [Al(H2O)5(OH)] 2+ + H+
OR
[Al(H2O)6] 3+ + H2O —> [Al(H2O)5(OH)] 2+ + H3O+
Reaction of [Fe(H2O)6] 2+ with Na2CO3
[Fe(H2O)6] 2+ + CO3 2- —> FeCO3 + 6H2O
green solution becomes green ppt FeCO3