18-24. Preparing standards for a calibration curve. (a) How much ferrous ammoniu

Question

18-24. Preparing standards for a calibration curve. (a) How much ferrous ammonium sulfate (Fe(NH)2 (SO4 FM 392.15) should be dissolved in a 500-mL volumetric flask wi 1 M H,so, to obtain a stock solution with 1 000 g Fe/mL? (b) When making stock solution (a), you weighed out 3.627 g of reagent. What is the Fe concentration in g Fe/mL? H.0. th (c) How would you prepare 250 mL of standard containing 1,2,3, 4, 5, 7, 8, and 10 (±20%) g Fe/mL in 0.1 M H2SO4 from stock solution (b) using only 5- and 10-mL Class A pipets, only 250-ml volumetric flasks, and only two consecutive dilutions of the stock solution? For example, to prepare a solution with ~4 g Fe/mL. you could first dilute 15 mL10 + 5 mL) of stock solution up 250 mL to get ~()(1 000 g Fe/mL) = ~ 60 gFe/mL. dilute 15 mL of the new solution up to 250 m -(,) (60 g Fe/mL) = ~ 3.6 g Fe/mL. go 18-25. Uncertainty in preparing standard solution. UsI Using uncea

Explanation / Answer

a. 392.15g of Fe(NH4)2(SO4)2.6H2O contains 56g of Fe. for 1 microg of Fe we need to have 1.42X10^-7g of ferrous ammonium sulphate.

here we need to have 1 Micro g Fe per ml of 500ml solution. so we need to have 500X1.42X10^-7g of ferrous ammonium sulpate.

b) 3.627g of Feerous ammonium sulphate will have 0.5179g of Fe. in order to make 1Microg/ml solution we need to add 517.9 ml water.

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