You weigh out 196.07mg ferrous ammounium sulfate (FW 392.14) to prepare 250mL of solution which is 0.002M with respect to that compound. The salt is quantitatively transferred into a 250mL volumetric flask and 8mL of 3M H2SO4 is added and then diluted to the mark (call this stock Fe solution). 10mL of the stock solution is pipeted into a 100mL volumetric flask, adding 4mL of 3M H2SO4 and diluted to the mark (call this original Fe solution).

10mL of the original fe solution is pipeted into a 50mL volumetric flask (call this standard Fe solution). What is the concentration of the standard Fe solution (mg/L)?

It should be somewhere around 2, but I can't seem to calculate it correctly.

You weigh out 196.07mg ferrous ammounium sulfate (FW 392.14) to prepare 250mL of solution which is 0.002M with respect to that compound.

The salt is quantitatively transferred into a 250mL volumetric flask and 8mL of 3M H2SO4 is added and then diluted to the mark (call this stock Fe solution).

So this 250 ml solution is

784.28 mg L^-1 (as FAS hydrate)
0.00200 M
112 mg L^-1 as Fe

10mL of the stock solution is pipeted into a 100mL volumetric flask, adding 4mL of 3M H2SO4 and diluted to the mark (call this original Fe solution)

Here we have dilutes by a factor of 10

So this 100 ml solution is

78.428 mg L^-1 (as FAS hydrate)
0.000200 M
11.2 mg L^-1 as Fe

10mL of the original fe solution is pipeted into a 50mL volumetric flask (call this standard Fe solution).

I presume this is made to the mark? In which case there is a further dilution by a factor of 5.

15.69 mg L^-1 (as FAS hydrate)
0.0000400 M
2.24 mg L^-1 as Fe

So perhaps the question is looking for the Fe concentration in mg L^-1?

(You should check my figures as I have rounded in places)

Um, exactly how did you calculate the 112 mg L^-1 as Fe, 11.2 mg L^-1 as Fe and 2.24 mg L^-1 as Fe ?

To calculate the concentration of the standard Fe solution, we need to follow the dilution process from the initial stock solution to the final standard solution. Let's break it down step by step:

1. Stock Fe Solution:
The stock solution is prepared by weighing out 196.07mg of ferrous ammonium sulfate and dissolving it in a 250mL volumetric flask. The Molar Mass (FW) of ferrous ammonium sulfate is given as 392.14 g/mol.
Using the formula:

Concentration (C) = (mass of solute)/(Molar mass x volume of solvent)

Concentration of stock Fe solution = (196.07 mg) / (392.14 g/mol x 0.250 L) = 0.198 M

2. Original Fe Solution:
10mL of the stock Fe solution is pipetted into a 100mL volumetric flask. 4mL of 3M H2SO4 is added, and the solution is diluted to the mark. This results in the original Fe solution.
Since the dilution is done by a factor of 10 (from 10mL to 100mL), the concentration of the original Fe solution will be 1/10th of the stock Fe solution concentration.

Concentration of original Fe solution = 0.198 M / 10 = 0.0198 M

3. Standard Fe Solution:
10mL of the original Fe solution is pipetted into a 50mL volumetric flask. This will be the final standard Fe solution.
Here, we need to apply another dilution. Since the dilution is done by a factor of 5 (from 10mL to 50mL), the concentration of the standard Fe solution will be 1/5th of the original Fe solution concentration.

Concentration of standard Fe solution = 0.0198 M / 5 = 0.00396 M

To convert this concentration to mg/L, we can use the formula:

Concentration (mg/L) = (Concentration (M) x Molar mass) x 1000

Concentration of standard Fe solution = (0.00396 M) x (392.14 g/mol) x 1000 = 1557.7 mg/L

Therefore, the concentration of the standard Fe solution is approximately 1557.7 mg/L.