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### G25

Posted: Sun Oct 08, 2017 12:19 pm
Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an affect. Is this claim plausible? To explore this question, suppose that you prepare a solution of an active substance X, with a molarity of 0.10 mol per liter. Then you 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?

### Re: G25

Posted: Sun Oct 08, 2017 3:47 pm
The molarity of the initial solution is 0.10 M. Every time you double the volume, the concentration decrease to half of its original concentration. Thus the molarity of the final solution would be 0.10* (1/2)^90. After you get the final concentration, multiply that by the volume and that will give you the moles of molecule, which you can then convert into number of molecules by multiplying the Avogadro's constant.