6: Reaction of Ions in Aqueous Solution Flashcards
How many H2O molecules bind to a metal ion?
6
How do we name metal aqua ions?
Hexaaqua for the 6 H2O
Then the metal name
Eg: Hexaaquacopper
What type of bonds are found in metal aqua ions?
Coordinate
Give 2 hydrolysis equations, starting with [Fe(H2O)6]2+, that show the acidity. The final product should be [Fe(OH)2(H2O)4]
[Fe(H2O)6]2+ + H2O = [Fe(H2O)5(OH)]+ + H3O+
[Fe(H2O)5(OH)]+ + H2O = [Fe(OH)2(H2O)4] + H3O+
Give 3 hydrolysis equations, starting with [Al(H2O)6]3+, that show the acidity of 3+ ions. The final product should be [Al(OH)3(H2O)3]
[Al(H2O)6]3+ + H2O = [Al(H2O)5(OH)]2+ + H3O+
[Al(H2O)5(OH)]2+ + H2O = [Al(OH)2(H2O)4]+ + H3O+
[Al(OH)2(H2O)4]+ + H2O = [Al(OH)3(H2O)3] + H3O+
Give 2 reasons why 3+ ions are more acidic.
They have a larger charger and are therefore smaller
3+ Ions are more polarising
What does it mean to say that 3+ ions are more polarising to water ligands?
They have a higher charge and therefore attract more electrons from the oxygen in the water molecule, in the coordinate bond
When OH- is added during hydrolysis, how does this affect equilibrium?
This removes H3O+ ions, so equilibrium shifts right to try and raise concentration of these ions.
Give an overall hydrolysis equation for [Fe(H2O)6]3+ with NH3
[Fe(H2O)6]3+ + 3NH3 = [Fe(OH)3(H2O)3] + 3NH4+
Give an overall hydrolysis equation for [Cu(OH)6]4- with NH3
[Cu(OH)6]4- + 4NH3 = [Cu(NH3)4(H2O)2]2+ + 6OH-
Give a general overall ionic equation for the hydrolysis of metal aqua ion [M(H2O)6]2+ using Na2CO3
[M(H2O)6]2+ + CO3 2- = MCO3 + 6H2O
What colour will the precipitate produced be when NaOH is added to a solution of Fe3+ ions?
Brown precipitate
Give the overall reverse hydrolysis equation for the formation of [Fe(H2O)6]3+ from Fe(OH)3(H2O)3
Fe(OH)3(H2O)3 + 3H+ =[Fe(H2O)6]3+
What does amphoteric mean?
Where a substance can act as both an acid or a base.
Give an equation for Al(OH)3(H2O)3 to form [Al(OH)4(H2O)2]- where it acts as a Bronsted Lowry acid.
Al(OH)3(H2O)3 + OH- = [Al(OH)4(H2O)2]- + H2O
Give an equation showing Al(OH)3(H2O)3 acting as Bronsted Lowry base.
Al(OH)3(H2O)3 + 3H+ = [Al(H2O)6]3+
If you add some OH- to [Fe(H2O)6]2+, what will you observe before and after?
What will you observe if OH- is added in excess?
Green solution to turns to green precipitate
No visible change
If you add some OH- to [Cu(H2O)6]2+, what will you observe before and after?
What will you observe if OH- is added in excess?
Blue solution to blue precipitate
No visible observation
If you add some OH- to [Fe(H2O)6]3+, what will you observe before and after?
What will you observe if OH- is added in excess?
Orange solution to brown precipitate
No visible observation
If you add some OH- to [Al(H2O)6]3+, what will you observe before and after?
What will you observe if OH- is added in excess?
Colourless solution to white precipitate
No visible reaction
If you add some NH3 to [Fe(H2O)6]2+, what will you observe before and after?
What will you observe if NH3 is added in excess?
Green solution to green precipitate
No visible change
If you add some NH3 to [Cu(H2O)6]2+, what will you observe before and after?
What will you observe if NH3 is added in excess?
Blue solution to blue precipitate
Deep blue precipitate
If you add some NH3 to [Fe(H2O)6]3+, what will you observe before and after?
What will you observe if NH3 is added in excess?
Orange solution to brown precipitate
No visible change
If you add some NH3 to [Al(H2O)6]3+, what will you observe before and after?
What will you observe if NH3 is added in excess?
Colourless solution to white precipitate
If you add some CO3 2- to [Fe(H2O)6]2+, what will you observe before and after?
Green solution to green precipitate
If you add some CO3 2- to [Cu(H2O)6]2+, what will you observe before and after?
Blue solution to blue/green precipitate
If you add some CO3 2- to [Fe(H2O)6]3+, what will you observe before and after?
Orange solution to brown precipitate with bubbles
If you add some CO3 2- to [Al(H2O)6]3+, what will you observe before and after?
Colourless solution to white precipitate and gentle bubbling
If you add excess acid to [Fe(H2O)4(OH)2], what will you observe before and after?
Green precipitate to green solution
If you add excess acid to [Cu(H2O)4(OH)2], what will you observe before and after?
Blue precipitate to blue solution
If you add excess acid to [Fe(H2O)3(OH)3], what will you observe before and after?
Brown precipitate to pale violet solution
If you add excess acid to [Al(H2O)3(OH)3], what will you observe before and after?
White precipitate to colourless solution
If you add excess alkali to [Fe(H2O)3(OH)3], [Fe(H2O)4(OH)2] and [Cu(H2O)4(OH)2] what will you observe before and after?
No visible change
If you add excess alkali to [Al(H2O)3(OH)3], what will you observe?
White precipitate to colourless solution
What is an acidic hydroxide?
A hydroxide that reacts with bases only.
What is a basic hydroxide?
A hydroxide that reacts with acids only.
Name the 3 basic hydroxides.
[Cu(H2O)4(OH)2]
[Fe(H2O)4(OH)2]
[Cu(H2O)3(OH)3]
State the observations you would see before and after adding excess Cl- to [Fe(H2O)6]2+
Green solution to yellow solution
State the observations you would see before and after adding excess Cl- to [Cu(H2O)6]2+
Blue solution changes to yellow
State the observations you would see before and after adding excess Cl- to [Fe(H2O)6]3+
Orange solution changes to yellow
State the observations you would see before and after adding excess Cl- to [Al(H2O)6]3+
Solution remains colourless
What is formed when you add Na2CO3 to [Al(H2O)6]3+?
What do you observe?
Give an equation.
Al(CO3)3(OH)3
Bubbles
2 [Al(H2O)6]3++ 3CO3 2–
-> 2 Al(H2O)3(OH)3 + 3H2O + 3CO2
Give a condition needed for the formation of [Al(OH)4]- from [Al(H2O)6}3+ and NaOH.
Give an equation.
Excess NaOH
[Al(H2O)6]3+ + 4 OH- ->[Al(OH)4]– + 6 H2O
Explain, with the use of an equation, why a solution containing [Al(H2O)6]3+ has a pH below 7.
[Al(H2O)6]3+ + H2O ⇌ [Al(H2O)5(OH)]2++ H3O+
Al3+ has a small size and high charge
This weakens the OH bond in water, releasing H+ ions
