Question

(a) How much ferrous ethylenediammonium sulfate (Fe(H3NCH2CH2NH3)(SO4)2 · 4 H2O, FM 382.15) should be dissolved in a 500-mL volumetric flask with 1 M H2SO4 to obtain a stock solution with ~500 µg Fe/mL? (Assume you are using a Class 1 analytical balance as seen in the Tolerances for Laboratory Balance Weights table. Enter an unrounded value.) Correct answer: 1.7106

(b) When making stock solution (a), you actually weighed out 1.650 g of reagent. What is the Fe concentration in µg Fe/mL? Correct answer: 482.28

(c) How would you prepare 500 mL of standard containing ~1, 2, 3, 4, and 5 µg Fe/mL in 0.1 M H2SO4 from stock solution (b) using any Class A pipets from the Tolerances of Class A Transfer Pipets table with only 500-mL volumetric flasks?

To prepare a 1 µg Fe/mL solution, dilute ? ml of stock solution from (b) up to 500 mL with 0.1 M H2SO4.

To prepare a 2 µg Fe/mL solution, dilute ? mL of stock solution from (b) up to 500 mL with 0.1 M H2SO4.

To prepare a 3 µg Fe/mL solution, dilute ? mL of stock solution from (b) up to 500 mL with 0.1 M H2SO4.

To prepare a 4 µg Fe/mL solution, dilute ? mL of stock solution from (b) up to 500 mL with 0.1 M H2SO4.

To prepare a 5 µg Fe/mL solution, dilute ? mL of stock solution from (b) up to 500 mL with 0.1 M H2SO4.

(d) To reduce the generation of chemical waste, describe how you could prepare 50.00 mL of standard containing ~1, 2, 3, 4, and 5 µg Fe/mL in 0.1 M H2SO4 from stock solution (b) by serial dilution using any Class A pipets from the Tolerances of Class A Transfer Pipets table with only 50.00-mL volumetric flasks?

First, make a 1:10 dilution by diluting ? mL of stock solution from (b) up to 50.00 mL with 0.1 M H2SO4.

To prepare a 1 µg Fe/mL solution, dilute ? mL of the dilute solution up to 50.00 mL with 0.1 M H2SO4.

To prepare a 2 µg Fe/mL solution, dilute ? mL of the dilute solution up to 50.00 mL with 0.1 M H2SO4.

To prepare a 3 µg Fe/mL solution, dilute ? mL of the dilute solution up to 50.00 mL with 0.1 M H2SO4.

To prepare a 4 µg Fe/mL solution, dilute ? mL of the dilute solution up to 50.00 mL with 0.1 M H2SO4. To prepare a 5 µg Fe/mL solution, dilute ? mL of the dilute solution up to 50.00 mL with 0.1 M H2SO4.

I really need help with C and D. Thanks in advance!

Answer 1

Answer:

a) To prepare a 500 ug/ml Fe solution

grams of Fe needed = 0.5 g/L or 0.25 g/500 ml

55.845 g Fe is in 382.15 g sulfate, so for 0.25 g = 1.711 g

So we need 1.711 g of (Fe(H3NCH2CH2NH3)(SO4)2 ·4 H2O to prepare the stock solution

(b) with 1.648 g weighed compound,
concentration of Fe in solution = 1.648 x 500/1.711 = 481.6 ug/ml

(c) To prepare 1 ug Fe/ml solution, dilute 1.04 ml of stock solution to 500 ml

To prepare 2 ug Fe/ml solution, dilute 2.08 ml of stock solution to 500 ml

To prepare 3 ug Fe/ml solution, dilute 3.12 ml of stock solution to 500 ml

To prepare 4 ug Fe/ml solution, dilute 4.16 ml of stock solution to 500 ml

To prepare 5 ug Fe/ml solution, dilute 5.20 ml of stock solution to 500 ml