This discussion is now closed.
Check out other Related discussions
- Inorganic Chemistry A Level- Help!
- transition metals
- Y13 GYG simple n straightfoward 🙌
- Is it a problem not knowing A2 inorganic and a lot of organic chem for oxford intervi
- chemistry inorganic reactions/colours/observations
- Electron Configuration of Zinc (Zn)
- Chemistry (Complex ions and aqua ions)
- A level chemistry aqa
- OCR Chemistry A-level predictions for paper 3?
- Year 13's, where is your school at with Chemistry AQA content?
- Free flashcards for OCR Chemistry A-Level
- Learning Transition metal complex ions.
- any a-level advice?
- Ds to As
- transition metals (a level chemistry)(help me)
- Ask Us Anything!
- What is your best technique for memorising content ?
- Anki Cards for Advanced Higher Chemistry + Physics
- Edexcel A-level Chemistry Paper 1 - 10th June 2025 [Exam Chat]
- Anyone know where I can find flashcards/resources for my biology + other subjects?
A2 Chemistry Transition Metals
Hi, could anyone help me with these Transition metal questions please ... I'm really confused about all these complexes. 
The bidentate ligand 1,2-diaminoethane, NH2CH2CH2NH2, reacts with an aqueous soultion of copper (II) sulphate to give a deep blue solution containing the ion [Cu(NH2CH2CH2NH2)2(H20)2]2+.
What's the oxidation state and coordination number of Cu in this ion? (Coordination number 4?)
What causes the colour change in this reaction? (Change in coordination number?)
Write an equation for the reaction. You may use "en" for NH2CH2CH2NH2. (I have no idea about this)
Can anyone help, please?
The bidentate ligand 1,2-diaminoethane, NH2CH2CH2NH2, reacts with an aqueous soultion of copper (II) sulphate to give a deep blue solution containing the ion [Cu(NH2CH2CH2NH2)2(H20)2]2+.
What's the oxidation state and coordination number of Cu in this ion? (Coordination number 4?)
What causes the colour change in this reaction? (Change in coordination number?)
Write an equation for the reaction. You may use "en" for NH2CH2CH2NH2. (I have no idea about this)
Can anyone help, please?
Right, I'll give this a go.
The complex they give you is a Cu2+ ion (still octahedral) with 2 water molecules still attached and to of these [en] ligands which attach in two places each (hence bidentate ... 2 teeth). If you can't picture this then let me know and I'll post a diagram.
The oxidation state of the Cu is still +2 (hasn't changed)
The coordination number is 6 (hasn't changed ... still ligands attached in 6 places, it just happens that 2 of the ligands are attached in 2 places each!)
Colour change:
This is to do with the splitting of the d orbitals - have you done this yet? The reason the colour changes is because the ligands change, and this changes the energy difference between the orbitals so the delta value changes and the energy of light (and hence colour) absorbed, changes.
Equation:
ligand displacement reaction:
(sorry I'm not bothering with subscripts / superscripts!)
[Cu(H2O)6]2+ + 2en ---> [Cu(H2O)2(en)2]2+ + 4H2O
If you still don't understand any of it, let me know.
The complex they give you is a Cu2+ ion (still octahedral) with 2 water molecules still attached and to of these [en] ligands which attach in two places each (hence bidentate ... 2 teeth). If you can't picture this then let me know and I'll post a diagram.
The oxidation state of the Cu is still +2 (hasn't changed)
The coordination number is 6 (hasn't changed ... still ligands attached in 6 places, it just happens that 2 of the ligands are attached in 2 places each!)
Colour change:
This is to do with the splitting of the d orbitals - have you done this yet? The reason the colour changes is because the ligands change, and this changes the energy difference between the orbitals so the delta value changes and the energy of light (and hence colour) absorbed, changes.
Equation:
ligand displacement reaction:
(sorry I'm not bothering with subscripts / superscripts!)
[Cu(H2O)6]2+ + 2en ---> [Cu(H2O)2(en)2]2+ + 4H2O
If you still don't understand any of it, let me know.
Reply 2
dfghj
OP
That's great, thanks. We haven't been through the details on the origin or colour quite yet, just that a change of ligand causes a change of colour.
A few things I was unsure about: when you have a complex like this [Co(NH3)6]Cl3 where are the Cl atoms positioned? Same for CoCl3.5NH3 -I'm not sure what the complex looks like (coordination number 6 and oxidation state 2+).
A few things I was unsure about: when you have a complex like this [Co(NH3)6]Cl3 where are the Cl atoms positioned? Same for CoCl3.5NH3 -I'm not sure what the complex looks like (coordination number 6 and oxidation state 2+).
Velouria
That's great, thanks. We haven't been through the details on the origin or colour quite yet, just that a change of ligand causes a change of colour.
A few things I was unsure about: when you have a complex like this [Co(NH3)6]Cl3 where are the Cl atoms positioned? Same for CoCl3.5NH3 -I'm not sure what the complex looks like (coordination number 6 and oxidation state 2+).
A few things I was unsure about: when you have a complex like this [Co(NH3)6]Cl3 where are the Cl atoms positioned? Same for CoCl3.5NH3 -I'm not sure what the complex looks like (coordination number 6 and oxidation state 2+).
The Cl- ions are not ligands in that compound ... they are the anions to go with the Co ions. In aqueous phase they will be free floating Cl- ions.
Reply 4
dfghj
OP
Ah okay, but the question says:
Suggest a structural formula for CoCl3.5NH3 which indicates the number of ligands around the cobalt ion.
Would this just be [Co(NH3)5]Cl3 or would it be [Co(NH3)5(H20)]Cl3 because it was a reaction of aqueous cobalt chloride with an excess of aqueous ammonia...?
Suggest a structural formula for CoCl3.5NH3 which indicates the number of ligands around the cobalt ion.
Would this just be [Co(NH3)5]Cl3 or would it be [Co(NH3)5(H20)]Cl3 because it was a reaction of aqueous cobalt chloride with an excess of aqueous ammonia...?
Reply 5
Only the chlorides can be balancing ions, so the five ammonia molecules must be ligands. This leaves one place available in the octahedral complex that must be occupied by one of the chlorides. The overall charge on the complex ion must then be 2+
[Co(NH3)5Cl]Cl2
in which the [Co(NH3)5Cl]2+ ion is balanced by two chloride ions Cl-
Cobalt pentaamminechloro III ion?
[Co(NH3)5Cl]Cl2
in which the [Co(NH3)5Cl]2+ ion is balanced by two chloride ions Cl-
Cobalt pentaamminechloro III ion?
Reply 7
Sorry Xskater, it's octahedral. Transition metals of the first row do not form 5-coordinate complexes...
Related discussions
- Inorganic Chemistry A Level- Help!
- transition metals
- Y13 GYG simple n straightfoward 🙌
- Is it a problem not knowing A2 inorganic and a lot of organic chem for oxford intervi
- chemistry inorganic reactions/colours/observations
- Electron Configuration of Zinc (Zn)
- Chemistry (Complex ions and aqua ions)
- A level chemistry aqa
- OCR Chemistry A-level predictions for paper 3?
- Year 13's, where is your school at with Chemistry AQA content?
- Free flashcards for OCR Chemistry A-Level
- Learning Transition metal complex ions.
- any a-level advice?
- Ds to As
- transition metals (a level chemistry)(help me)
- Ask Us Anything!
- What is your best technique for memorising content ?
- Anki Cards for Advanced Higher Chemistry + Physics
- Edexcel A-level Chemistry Paper 1 - 10th June 2025 [Exam Chat]
- Anyone know where I can find flashcards/resources for my biology + other subjects?
Latest
Trending
Last reply 2 days ago
AQA A level chemistry synthetic routes map - what is the best one to memorise?Last reply 3 weeks ago
is pcl5 and water nucleophilic or electrophilic substitution?Last reply 1 month ago
OCR AS Level Chemistry A Paper 2 - Depth ( 21th May 2024)
