Textbook G.25

[Chanel Mao 3D]

To explore this question, suppose that you prepare a solution of a supposedly active sub-stance, X, with a molar concentration of 0.10 mol/L. Dilute 10. mL of that solution by doubling the volume, doubling it again, and so on, for 90 doublings in all. How many molecules of X will be present in 10. mL of the final solution? Comment on the possible health benefits of the solution.

Hi! For this problem I got a final solution of 4.9 x 10^-7 molecules of X left, but the answer key says that there are no molecules of substance X left in the final solution. Am I doing something wrong?

[Charlene D 3H]

Hi Chanel,
This confused me as well. I think the textbook said "no substance" because the answer you got is very small and therefore insignificant and has no effect on a patient.
i hope this helped.

[Leo Naylor 2F]

To provide further clarification, your answer states that there is less than 1 molecule left, or really closer to 1 millionth of a molecule left. Molecules are indivisible (ignoring fission), so this small of a number indicates that there is no molecule remaining.

[Chanel Mao 3D]

Hi Chanel,
This confused me as well. I think the textbook said "no substance" because the answer you got is very small and therefore insignificant and has no effect on a patient.
i hope this helped.

Oh okay, thank you!!

[Chanel Mao 3D]

To provide further clarification, your answer states that there is less than 1 molecule left, or really closer to 1 millionth of a molecule left. Molecules are indivisible (ignoring fission), so this small of a number indicates that there is no molecule remaining.

That makes a lot of sense, thank you so much!