You extract the iron from a tablet and dilute that to 250.0 ml in a volumetric flask. You transfer 0.400 ml of this solution to a 25.0 ml volumetric flask and dilute this to volume. When you measure the concentration of this solution, you find that it is 3.27 ppm Fe. How many milligrams of Fe were in the tablet?

Question

You extract the iron from a tablet and dilute that to 250.0 ml in a volumetric flask.  You transfer 0.400 ml of this solution to a 25.0 ml volumetric flask and dilute this to volume.  When you measure the concentration of this solution, you find that it is 3.27 ppm Fe.  How many milligrams of Fe were in the tablet?

DrBob222 · Answer

I think the easy way to do this is to convert 3.27 ppm in the last sample to mg in that sample. We know 3.27 ppm = 3.27 mg/L and since this in 25 mL, then 3.27 mg/L x 0.025 L = 0.08175 mg in the 25 mL. That's also the mg Fe in the 0.4 mL. If 0.08175 mg are in 0.4mL, then 0.08175 x (250/0.4) = ? mg in the original sample.