Transition Metals Flashcards
What is a transition metal?
Metals that contain an incomplete d sub shell in at least one of their ions
Where are transition metals found?
In the ‘d block’ (middle, group 3)
Why are Sc and Zn technically NOT transition metals, despite being found in the d block?
They have no or complete d shells
Sc 3+ = [Ar] Zn 2+ = [Ar] 3d10
What is a ligand?
An atom or ion which donates a lone pair to form a co-ordinate bond to metal
What is a complex?
A metal ion with ligands co-ordinately bonded to it
What is the co-ordination number?
The number of co-ordinate bonds from ligands to the metal ion in the complex
What is a bidentate ligand?
A ligand which forms two co-ordinate bonds. Two different lone pairs on the molecule donate two electron pairs
Give 2 examples of a monodentate ligand
H2O: :OH- :NH3 :CN- :Cl
When can optical isomerism occur?
Can occur when bidentate ligands are attached to an octahedral complex
Give an example of a multidentate ligand
EDTA 4-, haem, [Pt(NH3)2Cl2] (cisplatin), [Ag(NH3)2]+
Why is EDTA 4- such an effective ligand?
It has 6 lone pairs, and so can form 6 points of attachment
[Cu(H2O)6]2+ is added with an unknown substance. The solution turns from light blue to dark blue. What was the unknown substance?
Ammonia
Ammonia is added to [Cu(H2O)6]2+. What are the products formed?
[Cu(NH3)4(H2O)2]2+ + 4H2O
Concentrated HCl is added to [Cu(H2O)6]2+. What are the products formed?
[CuCl4]2- + 6H2O
Ammonia is added to [Cu(H2O)6]2+. What is the colour change observed?
Light blue to dark blue
Concentrated HCl is added to [Cu(H2O)6]2+. What is the colour change observed?
Light blue to yellow
Concentrated HCl is added to [Cu(H2O)6]2+. The solution should turn yellow, but it looks more green. Why?
Because it’s going from blue to yellow
Ammonia is added to [Co(H2O)6]2+. What are the products formed?
[Co(NH3)6]2+ + 6H2O
Ammonia is added to [Co(H2O)6]2+. What is the colour change observed?
Pink to pale brown
Concentrated HCl is added to [Co(H2O)6]2+. What is the colour change observed?
Pink to dark blue
Concentrated HCl is added to [Co(H2O)6]2+. What are the products formed?
[CoCl4]2- + 6H2O
Why is the colour change so dramatic when concentrated HCl is added to [Co(H2O)6]2+?
The colour change is dramatic because the co-ordination number also changes (Cl is big so can’t fit round octahedral)
What is the chelate effect?
The substitution of monodentate ligands (eg H2O) by multidentate ligands
What is a use of a chelate?
It is useful in dealing with heavy metal poisoning, as it ‘cages’ up and so limits the poisoning effects
What is the equation to work out the energy change, using Plank’s constant and lamda?
Energy = hv where h = Plank’s constant and lamda = the speed of light/wavelength
What is Plank’s constant?
6.63 x10^-34 Js
What is the speed of light?
3x10^8 ms^-1
What are the factors that affect the size of energy gap?
The metal, the oxidation state, the ligands, the co-ordination number
Why are some substances able to give different colours/observations?
They have a variable oxidation state
KMnO4 is titrated against acidified Fe2+. What colour change is observed?
Colourless to pink
KMnO4 is used in a redox titration against acidified Fe2+. After all the acid has been used up, the colour change observed is brown/dark red rather than pink. What has happened?
There was not enough acid to full oxidise the MnO4-
Instead MnO2 formed
What colour is MnO4-?
Purple
A student is choosing an acid to acidify Fe2+ for a redox titration. The options are dilute H2SO4, conc H2SO4 and dilute HCl. Which acid should she choose? Give reasons why the others are unsuitable.
Should choose dilute H2SO4
Conc H2SO4 is an oxidising agent, but there is already an oxidising agent present
Dilute HCl - Cl could be oxidised (Cl2 gas), so the titration would larger and thus inaccurate.
The complex ion formed in aqueous solution between cobalt (II) ions and chloride ions is a different colour from the [Co(H2O)6]2+ ion. Explain why these complexes have different colours
Ligands are different and so cause different d orbital splitting. This means different amounts of energy are required to promote electron to the next energy level and so different frequencies of light are absorbed. Therefore different wavelengths/colours of light are transmitted
Fill the blanks. Heterogenous catalysts reactions often involve a ____ catalyst and _____ reactants.
solid catalyst and gaseous reactants
Describe alternate pathway a heterogenous catalyst provides
Reactants adsorbed onto the surface (active sites) - weakens bonds - brings molecules closer - more favourable orientation Reaction occurs Products desorbed
What is the issue if a catalyst bonds too strongly to a reactant?
It will never let go - both the catalyst and reactant will be unable to take part in the reaction
What is the issue if a catalyst bonds too weakly to a reactant?
If it bonds too weakly, it will not have the desired affects.
What is the contact process and which catalyst does it involve?
A way of producing H2SO4
Involves a vanadium (V) oxide catalyst
Give two half equations to show the contact process
SO2 + V2O5 –> V2O4 + SO3
V2O4 + 1/2 O2 –> V2O4
What is catalyst poisoning?
When the catalyst is covered by a substance which blocks the active sites, thus making it ineffective
Fill in the blank. Homogenous catalysts are mostly involved in reactions in a _____ with a catalyst in a _______
Solution for both
What is an autocatalyst?
A catalyst that is also one of the products of the reaction being catalysed.
Give a half equation showing the reduction of manganate
MnO4- + 8H+ + 5e- –> Mn2+ + 4H2O
Give two half equations to show the autocatalysis reaction of iodide ions and S2O8 2- to form iodine and sulphate ions
2I- + Fe3+ –> I2 + 2Fe3+
S2O8 2- + 2Fe2+ –> 2SO4 2- + 2Fe3+
Give 2 half equations to show the reaction of MnO4- with C2O4 2-
MnO4- + 8H+ + Mn2+ –> 5Mn3+ + 4H2O
C2O4 2- + 2Mn3+ –> 2CO2 + 2Mn2+
Give the formula of cisplatin
[Pt(NH3)2Cl2]
How many lone pairs are there on EDTA 4-?
6
Give the formula of ethanedioate
C2O4 2-
Give the formula of 1,2-diaminoethane
AKA en
H2N-CH2-CH2-NH2
