quick genchem question

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this might be elementary but....

how many atoms of carbon are in 4.00X10^-8 grams of C3H8?

 

[How Sleepy??!!]

You need to use dimensional analysis as follows: grams to moles, moles to molecules (Avogadro's number), and 3 atoms of Carbon per molecule of propane. That will give you the correct answer.

 

[haavoc]

Hi,

I was just doing this problem this morning in the barrons book, although it told me I was wrong.

Here's what I did:

(4x10^-8 g C3H8)(1 mol C3H8 / 44 g C3H8)(6 x 10^23 molecules C3H8 / 1 mol C3H8)(3 atoms C / 1 molecule C3H8)

Answer: 1.64 x 10^15 atoms C.

I don't think I did this problem incorrectly.

I think I'm going to ditch this book and stick to my Kaplan blue book and TopScore DAT.

 

[askadds]

thats exactly what I did and its incorrect. I think this is the 2nd question i have come by in the barron's that doesnt make sense....

the book says the answer is (E). 4.00x10^4