[aveecd]

OUr experminet is determining of iron: Dichromate process

volume of FeCl3 is 25ml
Volume of K2CrO7 is 25ml
Normality of K2CrO7 is 0.1 N
milligrams of fe = ?

the question is how to get the no. of milligrams of Fe in the total sample.

my answer is 67.1 mgs. Fe which i'm not sure of

the first thing i did was to convert the 0.1 N into molarity which would be 0.16667 M of k2CrO7

[Borek]

This is a little bit tricky.

1 N means it reacts with 1 mole of H⁺. Unfortunately, it is an ambiguous information. If it is about acid-base reaction (protonation of dichromate), 1 N means 1/2 M. If it is about redox, 1 N solution is 1/14 M.

Neither gives 67.1 mg of Fe.

Explain the operating procedure and show reaction equation.

[Hunter2]

Even more what confuses:  Iron-III-chloride and potassium bichromate don't react each other. If Iron-II-chloride is used then a redox reaction can take place.

[Borek]

Many procedures call for reduction in a first step, so while FeCl₃ raises a brow, it doesn't have to be wrong. That's why I asked for the details.

[tlahren]

The easiest way (and the way used in large scale Fe determination in iron ore mines) is to titrate a sample where you know the total amount of Fe (or Fe2+) in the sample.  Usually this is done on a NIST standard reference material (eg. NIST SRM 690 Canadian Iron Ore)  CofA: https://www-s.nist.gov/srmors/certificates/690.pdf?CFID=2265362&CFTOKEN=4333c583cb6f6c99-2CA03E75-FBEF-7BA5-2DAAD56BF0C5D9E9&jsessionid=f0304e911aff981ebe78145d22765374125d

For total iron about 0.4000 g of sample is dissolved in conc HCL on a hotplate to boiling for like 10 min (i don't remember the whole process) and is then cooled and diluted to a volume (~200 mL).  Add indicators and another stabilizing agent (somewhere in the process) and then titrate to endpoint with your dichromate solution.  Now you know X mLs of dichromate solution Means Y% Total Fe in 0.4000 g sample.  You end up with a calibration factor for your specific dichromate solution which you can use to back calculate the mLs of solution used to get %Fe.  The catch is that you have to do this every time you make a new dichromate solution to standardize it.  I suggest looking up the "Total Iron method" they refer to in the NIST certificate I listed above.  Hope this helps.