A2- Reactions in Aqueous Solution Flashcards
What is the colour of [Fe(H2O)6]2+ (aq)?
green solution
What are the observations when NaOH/dilute NH3 is added to aqueous Fe2+?
- green ppt goes brown on standing in air
What colour is FeCO3(s)?
When is it formed?
- green ppt
- action of Na2CO3(aq)
What is the colour of [Cu(H2O)6]2+ (aq)?
blue solution
What are the observations when NaOH/dilute NH3 is added to aqueous Cu2+?
- blue ppt
What is formed when aqueous Cu2+ reacts with an excess of concentrated ammonia?
[Cu(H2O)2(NH3)4]2+ (aq)
deep/royal blue solution
What colour is CuCO3(s)? When is it formed?
- blue-green ppt
- action of Na2CO3 (aq)
What colour is [CuCl4]2+?
green
What colour is [Fe(H2O)6]3+ (aq)?
purple solution
may look yellow-brown due to presence of some Fe(H2O)3(OH)3 (s)
What are the observations when NaOH/dilute NH3 is added to aqueous Fe3+?
- brown ppt
What colour is [Al(H2O)6]3+ (aq)?
colourless solution
What are the observations when NaOH/dilute NH3 is added to aqueous Al3+?
- white ppt
What happens when excess of NaOH is reacted with Aluminium (III)?
[Al(OH)4(H2O)2]- (aq)
white ppt redissolves
colourless solution
Why are aqueous metal ions acidic?
- metal ion is polarising
- attracts electron density off of the water ligands
- weakens O-H bond (allows H+ to be donated)
Why is Al3+ more acidic than Fe3+?
Al3+ is smaller
greater charge density
so greater polarising power
so O-H can be deprotonated easier
Why are 3+ ions more acidic than 2+ ions?
greater charge
so more polarising
so O-H can be deprotonated easier
What is the end product formed when aqueous Al3+ react with excess NaOH?
[Al(H2O)2(OH)4]-
Why are the end products (when reacted in excess) different in the reactions with NH3 and NaOH?
NaOH is a stronger base, whereas NH3 is not a strong enough base to further deprotonate
Give the 3 bases involved in these reactions in order of their strength…
OH- > NH3 > CO32-
What does NaCO3 deprotonate?
M3+ ions
What equation shows the action of NaCO3 reacting with aqua-metal 3+ ions?
2[M(H2O)6]3+ + 3CO32- –> 2M(H2O)3(OH)3 + 3H2O + 3CO2
What observation is made when M3+ ions react with NaCO3?
bubbles/effervescence due to CO2
colour change dependent on ion
Why do M2+ ions not form a metal hydroxide ppt when they react with NaCO3?
too weak and acid to react with the weak base NaCO3
What equation shows the reaction of NaCO3 and aqueous M2+ ions?
[M(H2O)6]2+ + CO32- –> MCO3 + 6H2O
