Transition metals Flashcards
Fe 2+ in aqueous solution
[Fe(H2O)6]2+ green solution
Cu 2+ in aqueous solution
[Cu(H2O)6]2+ blue solution
Fe 3+ in aqueous solution
[Fe(H2O)6]3+. pale violet solution but appears orange due to hydrolysis to some [Fe(H2O)5(OH)]2+
Al 3+ in aqueous solution
[Al(H2O)6]3+ colourless solution
Add aqueous NaOH dropwise to Fe2+
[Fe(H2O)4(OH)2] green precipitate (darkens on standing due to oxidation to [Fe(H2O)3(OH)3]
Add aqueous NaOH dropwise to Cu 2+
[Cu(H2O)4(OH)2] blue precipitate
Add aqueous NaOH dropwise to Fe3+
[Fe(H2O)3(OH)3] brown precipitate
Add aqueous NaOH dropwise to Al3+
[Al(H2O)3(OH)3] white precipitate
addition of excess aqueous NaOH to Fe2+
no further reaction form when was added dropwise
addition of excess aqueous NaOH to Cu2+
no further reaction form when was added dropwise
addition of excess aqueous NaOH to Fe3+
no further reaction form when was added dropwise
addition of excess aqueous NaOH to Al3+
[Al(H2O)2(OH)4]- re-dissolved to give colourless solution
adding aqueous NH3 dropwise to Fe2+
[Fe(H2O)4(OH)2] green precipitate which darkens on standing due to oxidation causing [Fe(H2O)3(OH)3]
adding aqueous NH3 dropwise to Cu2+
[Cu(H2O)4(OH)2] blue precipitate
adding aqueous NH3 dropwise to Fe3+
[Fe(H2O)3(OH)3] brown precipitate
adding aqueous NH3 dropwise to Al3+
[Al(H2O)3(OH)3] white precipitate
Adding excess aqueous NH3 to Fe2+
no further reaction form when it was added dropwise
Adding excess aqueous NH3 to Cu2+
[Cu(H2O)2(NH3)4]2+ deep blue solution
Adding excess aqueous NH3 to Fe3+
no further reaction form when it was added dropwise
Adding excess aqueous NH3 to Al3+
no further reaction form when it was added dropwise
adding aqueous Na2CO3 to Fe2+
FeCO3 green precipitate
adding aqueous Na2CO3 to Cu2+
CuCO3 blue-green precipitate
adding aqueous Na2CO3 to Fe3+
[Fe(H2O)3(OH)3] brown precipitate and bubbles of CO2 gas
adding aqueous Na2CO3 to Al3+
[Al(H2O)3(OH)3] white precipitate and bubbles of CO2 gas
adding concentrated HCl to Fe2+
[FeCl4]2- yellow solution
adding concentrated HCl to Cu2+
[CuCl4]2-green solution
adding concentrated HCl to Fe3+
[FeCl4]-yellow solution
adding concentrated HCl to Al3+
[AlCl4]- colourless solution
reaction between iodide ions and S2O8 2- catalysed by Fe
S2O8 2- + 2Fe2+ - –> 2 SO4 + 2Fe3+
2I- + 2Fe3+ - –> I2 + 2Fe2+
all arrows are reversible
reactions can occur either way round which is why Fe2+ or Fe3+ can be the catalyst
overall:
2 I- + S2O8 2- –> I2 + 2 SO4 2-
contact process
-catalysed by V2O5
V2O5 + SO2 –> V2O4 + SO3
V2O4 + 0.5O2 –> V2O5
overall:
2 SO2 + O2 –> 2 SO3
colours of vanadium ions oxidation state = +5
VO2 + yellow
colours of vanadium ions oxidation state = +4
VO 2+ blue
colours of vanadium ions oxidation state = 3+
V 3+ green
colours of vanadium ions oxidation state = 2+
V 2+ violet
haber process
3 H2 + N2 –> 2 NH3
reversible reaction arrow
reaction of ethanedioate ions and manganate ions
2 MnO4- + 16H+ + 5C2O42- –> 2 Mn2+ + 8 H20 + 10 CO2
catalysed by Mn2+ ions
reaction of manganate ions and iron ions
MnO4- + 8 H+ + 5 Fe 2+ –> Mn2+ + 4 H2O + 5 Fe 3+
role of iron as a catalyst in the haber process
Heterogeneous catalysts:
-heterogeneous catalyst which is in a different physical state to reactants
-catalyst speeds up rate of reaction by lowering activation energy by providing an alternative reaction pathway (left unchanged)
How to works on the haber process:
-hydrogen and nitrogen adsorb onto the surface (active sites) of the iron
-the bonds weaken and the reaction takes place
-the products desorb and leave the surface of the iron
How to increase/what affects efficiency:
-large surface area by using a powder or small pellets (or support medium/mesh)
-the catalyst is poisoned as the sulfur binds to the catalyst
-the active sites are blocked
what is an autocatalyst
a type of homogenous catalyst where the product is also a catalyst
how do heterogenous catalysts work
-different physical state to the reactants
-adsorbed onto the molecules active site and weakens the covalent bonds so reaction can occur more easily and rate is increased
-they can be poisoned by impurities which blocks the active site and prevents adsorption (so the bonds remain strong)
-reaction impurities increase chemical production costs as the catalyst has to be replaced or cleaned regularly
-rate can be increased by using a powder as increases surface area
why might there be impurities in the heterogeneous catalyst iron in the haber process
-the H2 is made from methane which contains sulfur impurities
-the sulfur will adsorb to the surface forming iron sulfide
-this makes the catalyst less efficient so needs to be cleaned or replaced often which is expensive
how do homogenous catalysts work
-same physical state as the reactants
-the catalyst combines the reactants to produce a reactive intermediate
-this changes the reaction pathway as the activation energy is initially high as two negative ions repel , so the enthalpy change for the formation of the intermediate is lower than the original reaction, so it is more feasible
oxidation of iodide ions catalysed by the homogenous catalyst iron
S2O8 2- + 2Fe 2+ –> 2Fe 3+ + 2SO4
-the intermediate Fe£+ produced catalyses
2I- + 2Fe 3+ –> 2 Fe 2+ + I2
reduction of VO2 (+) to V (3+) by Zn
charges in ()
2 VO2(+) + Zn + 4H(+) –> 2VO(2+) + Zn(2+) + 2H2O
yellow –> blue
2VO(2+ )+ Zn + 4H(+) –> 2V (3+) + Zn(2+) + 2H20
Blue –> green
2V(3+) + Zn –> 2V(2+) + Zn(2+)
green –> violet
