0.7957 g of ferrous ammonium sulfate hexahydrate are used to prepare the 100 ppm iron solution. Following the procedure described in the lab manual, what is the actual concentration of iron (in ppm) for the 7.0 ppm standard? Assume the density of water is 1.000 g/mL and express your answer with 4 sig figs.

From your working curve, absorbance (A) is related to concentration (c) through the function: A = 0.1944c + 0.0542. You measure the absorbance of your diluted sample to be 0.604. What is the concentration of iron in the undiluted unknown? (Express your answer with 4 significant figures.)

LAB procedure:

100ppm Iron Solution. In a 400mL beaker add 5mL of ^M HCL to about 250mL of water. Dissolve 0.7022g 9f ferrous ammonium sulfate in the acidified water. Transfer to a 1000mL volumetric flask aand dilute to the mark with deionized water. Mix well.

10 ppm Iron Solution. Pipet 50 mL of 100 ppm iron solution into a 500 mL volumetric flask. Dilute to mark with deionized water and mix well.