3.2.5 - Transition metals Flashcards
(25 cards)
Why is the reaction slow before a catalyst is added? (2)
- Negative ions repel
- Resulting in high activation energy
Why does s block not form catalysts?
They don’t have variable oxidation states
What determines pH level? (3)
- Charge to size ratio
- Greater ratio = more polarising = weaker O-H bond
- More H+ ions released
Hexa-aqua ions can dissasociate to produce H+ ions
Colours of iron2/3, copper, aluminium and their reaction products (except Cl- reaction)
Iron 2+ = Green
Iron 3+ = Brown
Copper = Blue
Aluminium = White
What is a bidentate ligand?
A ligand which binds to a metal in 2 different places via donation of 2 lone pairs
How are the coordinate bonds formed?
Ligand donates lone pair of electrons to central metal ion
What is the only ligand that forms tetrahedral complexes?
Chlorine
What shape does NH3 ligands form?
Octahedral
What isomerism do bidentate ligands exhibit?
Optical isomerism
What isomerism do square planar complexes exhibit?
Cis-trans
What isomerism do octahedral complexes exhibit? How do you determine which isomer it is?
- Cis-trans
- If the two odd ligands are opposite each other, it is trans
List all possible shapes of molecules and examples of each
- Octahedral (NH3/bidentates)
- Tetrahedral (chlorine)
- Square planar (cis-platin)
- Linear (silver)
Why are complex ions coloured? (3)
- Absorption of certain wavelengths of light
- Causes promotion of d-orbital electrons
- Remaining wavelengths reflected
Why might the enthalpy change of a reaction be very small/0? (2)
- Same types of bonds broken and made (i.e Cu—N)
- Same number of bonds broken and made
Why may a reaction become feasible? (3)
- Increase in number of particles
- Increase in entropy
- Free energy change becomes negative
Why is chlorine not a ligand?
It does not donate a lone pair
How does the iron catalyst in the Haber process work? (3)
- Reactants bind to active site of catalyst (adsorption)
- Reaction takes place
- Products desorb from catalyst
How can the iron catalyst become poisoned in the Haber process?
- Sulfur binds to catalyst
- Blocking active sites
How would you use colorimetry to determine the concentration of a sample? (3)
- Produce calibration curve
- By testing known concentrations of the sample with the colorimeter
- Compare the sample against the curve
What is the overall equation for the reaction between S2O8(2-) and I-?
Fe2+ is the catalyst for this reaction
S2O8(2-) + 2I- —–> I2 + 2SO4(2-)
What are the two reactions to show Fe2+ is a catalyst?
- S2O8(2-) + 2Fe(2+) —-> 2Fe(3+) + 2SO4(2-)
- 2Fe(3+) + 2I- —-> I2 + 2Fe(2+)
Fe2+ lowers the Ea because oppositely charged ions attract
What is the reaction between MnO4- and C2O4(2-)?
Mn2+ is the autocatalyst for this reaction, 2:5 ratio
2MnO4- + 16H+ + 5C2O4(2-) —-> 2Mn(2+) +8H2O + 10CO2
What are the two equations which show that Mn2+ acts as a catalyst?
- 4Mn2+ + MnO4- + 8H+ —-> 5Mn3+ + 4H2O
- 2Mn3+ + C2O4(2-) —-> 2Mn(2+) + 2CO2
Mn2+ lowers Ea beacuse oppositely charged ions attract
What is the equation of the reaction between Fe(2+) and MnO4-?
5:1 ratio
MnO4- + 8H+ + 5Fe(2+) —-> Mn(2+) + 4H2O + 5Fe(3+)
