Question

Suppose a 4.272 g soil sample undergoes an extraction with 50 ml of extracting solvent to remove the lead. This 50 ml was then diluted to 250 ml and tested by atomic absorption technique. The concentration of lead in this diluted extract was found to be 35.7 ppm. What is the lead concentration, in ppm, in the untreated soil sample?

Is this as simple as 35.7 ppm x 5 times dillution = 187.5 ppm?

Answer 1

Yes but you didn't multiply right. (rather, I think you transposed the numbers)

Answer 2

Thanks so much. You are correct the answer should read 178.5 ppm.

Answer 3

Could someone please clarify. I recently sent this question to the forum and thought I had it figured out. Now another student has told me to do this:
35.7 ppm x 250ml = 8.925 x 10-3 g
8.925 x 10-3 g/4.272g=2.089 x 10-3 = 2089 x 10-6 = 2089ppm

Please help I do not know what is the correct way of completing this question.