# AAMC 5 Question

Discussion in 'MCAT Discussions' started by 5moreminutes, Apr 21, 2007.

1. ### 5moreminutes Junior Member

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QUestion # 14 Physical Sciences

nCDP <-> CPn + nHPO42-

according to this equation, the concentration of the polymer with respect to (HPO4)2- is ?

And the answer is 1/n [HPO4]2-..
I just dont get it even after reading the explanation.
anyone have any insight on this one ?

THanks!

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3. ### GTsquirrel

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nCDP <-> CPn + nHPO42-

Okay, so you have to first understand the equation. The equations says that n molecules of the compound CDP (a diphosphate) (left side) will form one long polymer (with a total of n monomers) of CP (a monophosphate). So imagine n molecules of CP strung together like a pearl necklace, but keep in mind that this is still ONE molecule. The last part says that for every n molecule of CDP you use in the reaction, you will produce n molecules of HPO42-. So, let's say you use 10 molecules of CDP in the reaction. You will produce 10 molecules of HPO42- but only ONE molecule of CPn that consists of 10 monomers. You will always get one CPn for each reaction, but you will get n molecules of HPO42-. So, to determine how many molecules you get of CPn (which is always 1), you take the number of HPO42- molecules (which will always be n times greater than CPn) and divide it by n because n/n is 1.

Hope this helps.

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4. ### 5moreminutes Junior Member

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thanks,that does make sense, but its more of a math problem then physics , i guess

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