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# iron in sample

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How many milligrams of iron are in the sample? See attached file for full problem description.

https://brainmass.com/chemistry/physical-chemistry/iron-in-sample-105013

#### Solution Preview

First, we have to do is find the molar mass of ferrous ammonium sulfate hexahydrate in order to determine how much actual Fe is in the standard solution.

I calculate it as 296.1 g/mol. Check this out yourself.

Next, we need to find out what percentage the Fe is of the whole compound. Molar mass of Fe is 55.847 g/mol. Therefore,

(55.847/296.1) x 100% = 18.86%

Therefore, if we put in 70.2 mg (0.0702 g) of the compound, we have only 18.86% of that as Fe, right? That means we have:

70.2 mg x 0.1886 = 13.24 mg Fe(II) in the 1 L flask.

Therefore, the concentration of Fe(II) in that flask is:

13.24 mg/1000 mL = 0.01324 mg/ml

Now, we work through the dilutions.

The 1st standard solution results from taking 1 mL of this stock solution and diluting to 100 mL. That's a 1:100 ...

#### Solution Summary

It finds the mass of iron in sample

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