Edexcel Unit 5 Revision Notes

Hi, here are the notes I made on topics 5.1 (redox equilibria) and the dreaded 5.2 (transition metals). Included is a nice table of the precipitate colours of the transition metal hydroxides to learn from.

I will be making notes on topic 5.5 too - its quite hard to do benzene and reaction mechanisms on the computer and I already know all the kinetics stuff so I'm not gonna bother doing those.

Good luck revising! Im sure you are all feeling the strain...but not long to go now!

Unit 5.1 and 5.2.doc73.7KB

Reply 1

kpg

11

You can't leave out the water ligands when writing equations for transition metals, or atleast so we've been told. You ALWAYS need to write out the full ion for transition metals apparently.

edit ; I'm also sure Zinc forms a colourless solution in excess OH and ammonia

Reply 2

raam001584

great notes!!!

...just one think in excess NH3 is this ligand exchange as NH3 displaces H20 and
in copper II hydroxide why does the solution with excess NH3 only have 4 NH3 compared with 6 in the other reaction

thanks in advanced

Reply 3

KP Nuts

OP

1

raam001584

great notes!!!

...just one think in excess NH3 is this ligand exchange as NH3 displaces H20 and
in copper II hydroxide why does the solution with excess NH3 only have 4 NH3 compared with 6 in the other reaction

thanks in advanced

Im not sure why this happens, but it is what the NAS textbook says, so thats what im learning.

And to the person that said that zinc hydroxide also dissolves in ammonia - that is probably correct - i couldnt find much in the textbook

raam001584

great notes!!!

...just one think in excess NH3 is this ligand exchange as NH3 displaces H20 and
in copper II hydroxide why does the solution with excess NH3 only have 4 NH3 compared with 6 in the other reaction

thanks in advanced

Copper is a little strange in that its 'haxaaqua' ion is really square planar [Cu(H2O)4]2+ with two axial water ligands much more loosely bound.
This is due to something called the Jahn-Teller effect.

The higher transition metals tend to form tetrahedral or square planar complexes by hybridising the 4sº and 4p orbitals to accept electron pairs as all the '3d' orbitals are already full (or partly so)

The ammonia exchnges with the tightly bound water molecules to make the tetraammine complex but also probably has loosely bound axial ligands whose identity depends on the relative concentrations of available species in solution.

All this is on a not-need-to-know basis :smile:

Reply 5

KP Nuts

OP

1

Cheers charco, chemguide.co.uk agrees! And ive uploaded the ammended version to show that a tetraamminezinc (II) complex is formed in excess NH3.

Reply 6

senshi

ooooo thnks for these. Rep for u :biggrin:

Reply 7

kpg

11

KP Nuts

Im not sure why this happens, but it is what the NAS textbook says, so thats what im learning.

And to the person that said that zinc hydroxide also dissolves in ammonia - that is probably correct - i couldnt find much in the textbook

The Nelson book is a bit wishy washy at times yup. Shame because that's all I used for my unit 4 exam and it worked fine.

Reply 8

raam001584

thanks for the info
dont need to know but at least i get it now

Reply 9

simiddd

I havent revised yet and i need an a, can any1 suppply any notes for the whole thing

Reply 10

kpg

11

If you haven't revised yet you're unlikely to get an A in two days to be honest. Best to concentrate on trying to learn the basic colours/reactions already posted and the reaction mechanisms.

Edexcel Unit 5 Revision Notes

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