[inexile96]

Hi guys, i have a few question for this experiment which i done in school.

Fe3+ + SCN-  [FeSCN2+]
Reagent used Fe(NO3)3 and KSCN both 0.002M and HNO3 0.10M

In this experiment Nitric acid, HNO3 was used to top up to mark. My question is what is the purpose of nitric acid? Can i use water instead?

My lecturer told me to repeat the experiment using DI. H2O instead of HNO3.

In the experiment using HNO3 the max wavelength absorption i obtain was 445nm in the spectrum scan and i was able to calculate the Kc value
But when i used H2O instead i am not able to determine any max wavelength absorption as the gradient was too steep from the graph.

My lecturer also told me that there are isomers in [FeSCN2+]  which i know that SCN- is a ambidentate ligand which Fe can bind to either Nitrogen or Sulfur. My next question is that does using DI.H2O cause formation of [FeNCS2+] and does [FeNCS2+] absorb similar wavelength as [FeSCN2+] .?

[orthoformate]

This is not my area of expertise, but wouldn't using DI water protonate the SCN^- and give HSCN? If protonation occurred then of course bonding at the nitrogen would be more likely.

Also, could you have issues with Fe(OH)₃ when using water?

good luck, this sounds interesting.