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# complex compound watch

1. Hi can someone please tell me how to get the answer on part d)ii)?
2. Why not just AgNCO?

3. (Original post by alow)
Why not just AgNCO?

I'm wondering why is that not the answer too. But the one i wrote is exactly the answer on the marking scheme
4. (Original post by Snowie9)
I'm wondering why is that not the answer too. But the one i wrote is exactly the answer on the marking scheme
It's a suggest question so I bet you would get the marks for either, as both can be linear.
5. (Original post by alow)
Why not just AgNCO?

AgNCO is not a complex and not linear.
6. (Original post by TutorsChemistry)
AgNCO is not a complex and not linear.
That's irrelevant. Unless the specific example was taught, there's no reason for an A Level student to not think AgNCO is a linear complex.
7. (Original post by alow)
That's irrelevant. Unless the specific example was taught, there's no reason for an A Level student to not think AgNCO is a linear complex.
Ar A level students should know that linear complexes have 2 ligands.
It is always relevant to answer the question and not just pick some words from the question, ignoring what isn't liked.
8. (Original post by TutorsChemistry)
Ar A level students should know that linear complexes have 2 ligands.
It is always relevant to answer the question and not just pick some words from the question, ignoring what isn't liked.
I see thanks! So for tetrahedral there's four?
9. (Original post by Snowie9)
I see thanks! So for tetrahedral there's four?
Yes. Also 4 in square planar.
6 in octohedral.

Usually when questioning about complex shapes the ligand will be monodentate, like your example ligand.
Just be aware to watch for polydentate ligands.
10. (Original post by TutorsChemistry)
Yes. Also 4 in square planar.
6 in octohedral.

Usually when questioning about complex shapes the ligand will be monodentate, like your example ligand.
Just be aware to watch for polydentate ligands.
I see. How do you write the charge of the complex?
11. Put a square bracket around the entire formula, and the charge after the closing bracket
12. (Original post by TutorsChemistry)
Put a square bracket around the entire formula, and the charge after the closing bracket
I wanna ask how to do this question too, i'm really weak in these type of questions and i'm having my A2 chem next week. It would be really great if you could help me out ):
13. The table or the stability constant part?

Hint: Double check the coordination number of the iron complex. Is the ethanedioate ligand monodentate or bidentate?
14. (Original post by TutorsChemistry)
The table or the stability constant part?

Hint: Double check the coordination number of the iron complex. Is the ethanedioate ligand monodentate or bidentate?
The table. I see it now based on what you told me earlier but i do not understand complex D. I know the ligand is neutral and therefore the charge is +2 but why the ligand have to be 3?
15. (Original post by Snowie9)
The table. I see it now based on what you told me earlier but i do not understand complex D. I know the ligand is neutral and therefore the charge is +2 but why the ligand have to be 3?
For D the ligand isn't neutral. It has a 2- charge per ion.
This ligand is bidentate, so forms 2 coordinate bonds per ligand to the iron ion. The coordination number for iron in this complex is 6 (3 ligands providing 2 coordinate bonds each).

The ligand is the ion of the dicarboxylic acid ethandioic acid (also called oxalic acid).
16. (Original post by TutorsChemistry)
For D the ligand isn't neutral. It has a 2- charge per ion.
This ligand is bidentate, so forms 2 coordinate bonds per ligand to the iron ion. The coordination number for iron in this complex is 6 (3 ligands providing 2 coordinate bonds each).

The ligand is the ion of the dicarboxylic acid ethandioic acid (also called oxalic acid).
Are you talking about complex D? D has Nickel
17. Sorry, my mistake.

The ligand in D is also bidentate, eacg ligand molecule makes 2 coordinate bonds with the nickel ion. The bond is from the lone pair on each nitrogen atom.
As there are 2 coordinate bonds per ligand, only 3 ligand molecules are required to satisfy the coordination number of 6.
18. For D: Coordination number is 6 - 6 lone pairs, therefore it is an octahedral complex.

H2NCH2CH2NH2 is a bidentate ligand, therefore you need 3 of these to fulfill the coordination number 6 as the N atom has 2 lone pairs on each (2x3=6)
19. (Original post by TutorsChemistry)
Sorry, my mistake.

The ligand in D is also bidentate, eacg ligand molecule makes 2 coordinate bonds with the nickel ion. The bond is from the lone pair on each nitrogen atom.
As there are 2 coordinate bonds per ligand, only 3 ligand molecules are required to satisfy the coordination number of 6.
I see! Thanks!!
20. (Original post by ChemistryGuy1998)
For D: Coordination number is 6 - 6 lone pairs, therefore it is an octahedral complex.

H2NCH2CH2NH2 is a bidentate ligand, therefore you need 3 of these to fulfill the coordination number 6 as the N atom has 2 lone pairs on each (2x3=6)
Thank you! I got it now

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