Question 1a) Will the two compounds produce peaks with the same retention time? Explain you answer.
It should be sufficient to say that because you have a molecule with a different structural connectivity (despite having the same chemical composition), then one of these molecules is different in chemical and physical properties to the other (and hence interacts differently with the mobile and stationary phase in GLC). You shouldn't need to state which one is more polar, although it is nice to know (use your commonsense here, the -OH group exposed on the ethanol is more polar than the C-O-C bridge that is surrounded by other atoms).
Question 2a) What amount, in mol, of fluoride is present in 1.0g if Melbourne water?
Don't be confused by the "microgram by gram" notation. It means "one microgram" of A per "gram" of B. Scaling this up by a factor of
reveals that this proportion is exactly the same as the "parts per million" notation: one gram of A per million grams of B. Note that "ppm" is in terms of grams - gladly assume this unless you are told otherwise.
In this case, "A" is fluoride ions and "B" is water, so using
, we know that per gram of water:
} = \frac{0.90 \times 10^{-6}\mbox{ g}}{19.0\mbox{ gmol}^{-1}} = 4.74 \times 10^{-8}\mbox{ mol})
b) How many fluoride ions would you swallow if you drank a 200 mL glass of Melbourne water?
Using the density of water:
, we can say that if there is
} = 4.74 \times 10^{-8}\mbox{ mol})
per gram of water, then in 200mL (200 grams) of water, there are:
}_{\mbox{200 mL}} = 4.74 \times 10^{-8} \times 200 = 9.47 \times 10^{-6}\mbox{ mol})
Now, it says "how many fluoride ions," so you have to actually give the number of ions, rather than in terms of moles:
} = 9.47 \times 10^{-6} \times 6.02\times 10^{23} = 5.70 \times 10^{18})
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