REDOX/TRANSITION METALS Flashcards
What is a transition metal
Forms at least one stable ion with partially filled d sub shell
What key features do transition metals have
Form complex ions
Coloured ions
Catalytic properties
Variable oxidation states
Define a coordinate bond
Shared pair of electrons which have both come from the same atom
What is a ligand
An ion or molecule with a pair of electrons which can form a coordinate bond with a transition metal ion
What is a Bidentate ligand
Molecule with two atoms with pairs of electrons available to form coordinate bonds with transition metal ion eg C2O4
What’s a complex ion
Central atom or ion surrounded by lignands
What’s a coordinate number
Number of coordinate bonds a transition metal ion can make
What is a multidentate ligand
Each ligand forms two or more coordinate bonds
What are the four common shapes transition metal complexes form
Octahedral eg [Cu(H2O)6]2+
Tetrahedral eg [CuCl4]2-
Square planer eg [Pt(NH3)2
Linear eg [Ag(H2O)2]+
Ligand substitution reaction example
Show how the complex [Cu(H20)6]2+ can be converted into [Cu(H2O)3(NH3)3]2+
[Cu(H2O)6]2+ + 3NH3 -> [Cu(H2O)3(NH3)3]2+ + 3H2O
When does the chelate effect occur
When a monodentate ligand is substituted out by a multi or Bidentate ligand
Cisplatin as cancer treatment
Binds to DNA in cancerous cells
Prevents DNA from unwinding so cancer cell can not replicate
Prevents growth and spread
Two Cl- ions on cisplatin substitute two N atoms on adjacent guanine bases
Why are transition metals coloured
Transition metal have a partially filled d sub shell
These electrons absorb specific amount of energy from visible light and transmits the rest
Electron d sub shell electrons become excited move from ground stable state to excited unstable state
Roy and biv
Small e Roy - smaller energy waves, longer wavelength
big e biv- higher energy waves, short wavelength
Changes that can alter the colour of compounds
Change in ligands
Change in oxidation state
Change in coordination number
Change in shape
LOCoS
Oxidation is….
Loss of electrons
Reduction is……
Gain of electrons
What is a oxidising agent
Accepts electrons
Its being reduced
What is a reducing agent
Loses electrons
Its being oxidised
Degine oxidation state
Number assigned to atomd in a compund to follow which elements are gaining ir losing electrons in a reaction
Oxidising state of
H
G1 metals
G2 metals
Al
O
F
Cl
H: +1
G1: +1
G2: +2
Al: +3
O: -2 (unless peroxide (H2O2) or bonded wiv F)
F: -1
Cl: -1 ( +1 if bonded with F or O)
How to find concentration of an unkown sample from the calibratrion curve(3marks)
Measure abosorbance for a randfe of known concentration
Plot a graph of absorbance against concentration against cruve
Read the value of the concentration for the measured absorbance from the graph
Heterogeneous catalyst
Catalyst is in a different phase to the reactant
Homogeneous catalyst
Catalyst in the same phase as reactant
Mechanism of heterogeneous catalysis (3marks)
Reactant adsorb onto surface of the catalyst on an active site
Reaction accurs on the surface of the catalyst
Products desorb from the surface of the catalyst
Making catalysts more efficient
Increase surface area
Spread the caatlyst over an inert support medium
Why cant catalyst last forever
Impurities blick active site
Prevents reactant from adsorbing
Purifying the reactant is the best way to prevent poisoning
Heterogeneous catalyst equations + catalyst
1. Making Ammonia in the Haber Process
2. Making Sulfuric Acid in the Contact Process
3. Manufacture of Methanol
- N2(g) + 3H2(g) <———-> 2NH3(g)
Catalyst- IRON
2.
SO2(G) + V2O5(S) <———> SO3(G) + V2O4(S)
2V2O4(S) + O2(g) <———>2V2O5(S)
Overall equation: 2SO2(G) +O2(G) ——-> 2SO3(G)
Catalyst- Vandium(V) oxide - CH4(G) + H2O(G) ——> CO(g) +3H2(g)
CO(G) + 2H2(g) ——> CH3OH(G)
Catalsyt- chromium (III) oxide (Cr2O3)
Homogenous catalyst equations
S2O8 2- (AQ) + 2I-(AQ) ——>2SO4 2- (AQ) + I2(AQ)
2 step porcess
S2O8 2-(AQ) + 2FE2+(AQ) ——-> 2SO4 2-(AQ) + 2FE3+ (AQ)
28-(AQ) + 2FE3+(AQ) ——> I2(aq) +2FE2+HAQ)
Autocatakysys mechanism (4 marks)
Rate start off slow as no catalyst present
2 negatively charged reactant collide with very high Ea
As Mn2+ formed rate increases as the reaction is bejng increasingly catalysed
Rate then decreases and levels off as the reactant get used up
Autocatalysis equation
2MnO4- + 16H+ +5C2O4 2- —-> 2Mn2+ +8H2O +10CO2
