[LeonardPagliaro]

Hello Everyone!

Here is my problem... I have performed iodometric titration on a NiOOH sample that I synthesized and I am not sure I am calculating the O.S. correctly.  Here are my knowns.  1% starch was used as an indicator.

1) Weight of NiOOH sample --> 0.02 g exactly
2) Excess KI and H2SO4
3) Average amount of 0.1 M sodium thiosulfate titrated at endpoint --> 2.1725 mL

Reactions:
1) 2 to 1 ratio of NiOOH to I2 in the nickel reduction reaction from 3+ to 2+
2) 1 to 2 ratio of I2 to thiosulfate in the iodine reduction reaction

So in the end it is a 1 to 1 ratio of NiOOH to sodium thiosulfate titrated meaning we have approx. 0.000217 moles reacting.  When I performed my own calculations, I got an oxidation state between 3.04 to 3.05.  NiOOH O.S. can range from 2.95 to 3.55.  I need someone to confirm to me my calculations are correct and for them to tell me their procedure.  Thank you so much for your help.

I can also perform a complexometric titration to determine the nickel content if it is recommended.

[Hunter2]

I think the calculation is ok.

[LeonardPagliaro]

How would you do it?  I have never done these types of calculations and even though I got an O.S. between the accepted amount I am afraid that I am manipulating my numbers to give me an acceptable answer.  From the iodometry I can only find how much NiOOH was reacting with the KI.  I am not sure I am making the right jump to the oxidation state.