Question about E.35

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Jessica Lutz 2E
Posts: 56
Joined: Fri Sep 29, 2017 7:04 am

Question about E.35

Postby Jessica Lutz 2E » Thu Oct 05, 2017 11:49 am

The problem is: The decay of teeth can be slowed by the use of fluoridated toothpaste. The fluoride ions convert the hydroxyapatite, Ca5(PO4)3OH, in tooth enamel into fluorapatite, Ca5(PO4)3F.
If all the hydroxyapatite is converted into fluorapatite, by what percentage does this conversion increase the mass of the enamel?

I know that you are supposed to find the molar mass of each and then do (504.3-502.31)/504.3, but I don't know why that equation is what you use to find the percentage mass increase. Why do you not divide by 502.31 instead?

Hannah Guo 3D
Posts: 56
Joined: Fri Sep 29, 2017 7:06 am

Re: Question about E.35

Postby Hannah Guo 3D » Thu Oct 05, 2017 12:52 pm

percentage mass increase = change of mass/initial mass
So what you understand is correct, the calculation should be (504.3-502.31)/502.31*100%

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