FL9 #9 bio/biochem section

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FL9 #9 bio/biochem section

Post by jumpinfeet » Fri Sep 08, 2017 3:49 pm

I am still confuse by this problem. How did you get "dissolved particles by a factor of 1.5"? I get 2 for the 1 M KCl (split K and Cl). Am I missing something?
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Re: FL9 #9 bio/biochem section

Post by NS_Tutor_Andrew » Fri Sep 08, 2017 6:55 pm

Hi jumpinfeet,

Very good question! I think you might be missing the need to account for the volume of the KCl solution -- the question says that you add "an equal volume of 1 M KCl solution", not that you dissolve KCl in the original solution until you reach a concentration of 1 M. This means that the new solution has double the volume of the original one and three times the concentration of solvents. It may be helpful to work through this with easy (although unrealistically large) numbers -- let's say that the original solution had 1 mole of glucose in 1 L solvent, so the combined molarity (iM) = 1 M. In the new solution, we will have 3 moles of solute (1 mol K+, 1 mol Cl-, 1 mol glucose) in 2 L of solvent, so the combined molarity (iM) = 3/2 = 1.5 M. Hence the factor of 1.5.

Hope this helps, and feel free to reach out w/ further follow-up!
Andrew D.
Content Manager, Next Step Test Prep.
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