9 A student wanted to determine how much iron was present in

9. A student wanted to determine how much iron was present in 1.50 g of asparagus. She used a spectrometric method using a 1.00 cm cuvette to measure total iron concentration in her sample and obtained an absorbance of 0.555 at 447 nm. A set of standard iron solutions yielded the calibration plot shown below. What is the concentration of her sample? 1.2 y = 20245x-0.0001 R2 = 0.9908 a 0.8 0.6 40.4 0.2 0 0 0.00001 0.00002 0.00003 0.00004 0.00005 Concentration (M) (a) 1.24 x105 M (b) 1.83x105 M (c) 2.74 x10-5 M (d) 1.12 x104 M (e) 3.65 x104 M

Solution

9) option C)

Absorbance = 0.555

path length = 1.00 cm

extinction coefficient = 20245

A = e C x l

0.555 = 20245 x C x 1.00

C = 2.74 x 10^-5

concentration C = 2.74 x 10^-5 M