Vicky Silviana的实验室

You know, even the Second Hospital cannot contain me... We have gained much knowledge about these compounds so now we just need to deal with specific properties of these elements. Co2+ is very air-stable in weak field ligand environment, and [Co(H2O)6]3+ lies much higher than O2 so air would never oxidize it. However when the field strength increases(even to NH3) Co3+ quickly dominates since d6 is much more preferred than d7 in a low-spin configuration, the latter has an extra electron. Fe2+, on the other hand, is very air-sensitive unless in strongly acidic solution, or with strong field ligands like CN-. Although NO2- is also a strong field ligand, it cannot stop oxidation to hydrated Fe2O3 at all as shown below. Of course, besides oxygen, HNO2 can also oxidize these low-valent complexes, and is much more effective as shown in previous experiments. K2Ba[Co(NO2)6] Mixed acetate solution prepared as the Ni one mentioned before(in fact Co dissolves in H2SO4 even at RT so this is quite e...

 An electrolysis cell is a container with two electrodes in it. In order to be effective we need partitioning: carefully hit a test tube at ground to remove its bottom, and add glass wool in it. Here we do reduction so anode is inside, cathode is outside. V2+ is very reducing so use paraffin liquid above solution. In a short period, about a few days, you get purple solution which is the end. Heat this solution with excessive ammonium sulfate and magnesium sulfate (V:(NH4)2:Mg=1:5:4)then cool, then you get purple crystals. Similar procedure however, can't dye alums due to unknown reasons. Probably, different ion radius or wrong temperature? (Cooling also failed and solution freezing is driving me mad) to be continued...

 Welcome back! Now, let's first dissolve some CoSO4 or MnSO4 into 5M sulfuric acid, together with ammonium alum. To do so, add 0.02 mol of ammonium sulfate and aluminium sulfate to 100mL of acid, then 0.02 mol of the transition metal one. Now heat to dissolve these all, then cool down for a night to let excess alum crystallize. They are just alum of course. From now on different strategies are needed for them. Mn: Mn3+ is stable when H+ is very concentrated and Mn2+ is much more concentrated than Mn3+, so we should electrolysis without partitioning, and only a little part of Mn2+ is oxidized. Finally solution looks like this: Finely red. Cool this solution down to 0 degree celcius or so gives orange crystals, and throwing alum into initial solution gives it a cover. All crystals MUST be dried carefully! Solution can be used again of course. It seems that crystals are unstable when [Mn3+] is too high. This is hard to control. Reduction is simple though, just carefully add oxalic aci...

About the ions Although +3 oxidation state exists for all transition metals between Sc and Co, they are almost always unfriendly. While the common Cr3+ is stable and Fe3+ is mildly oxidizing and highly acidic, the closely related Mn3+ and Co3+ are exceedingly unstable at normal ranges. Instead of directly telling you the phenomena I'd like to show thermodynamic data first. E0(Mn3+/Mn2+)=+1.49V E0(MnO2/Mn3+)=+0.95V E0(Co3+/Co2+)=+1.92V E0(O2/H2O)=+1.229V The first two lines may need an explanation: if we make a battery of the first minus the second, it turns out that Mn3+ can release much electricity(energy) when it becomes Mn2+ and MnO2, as the net potential is highly positive, about +0.5V. That is to say, Mn3+ is very prone to disproportionation. The third line could just be called horrible: Co3+ is much higher than O2, so oxidizing water is quite easy! In fact this is just at pH=0 or [H+]=1mol/L, and things become much worse at neutral pH as H+ lies on the right side of the equat...