A sample of propane, C3H8, contains 17.9 moles of carbon atoms. How many total moles of atoms does the sample contain?

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Fortis Paradise Profile
Fortis Paradise answered

There are 3 moles of Carbon + 8 moles of Hydrogen= 11 moles of atoms

(11 moles of atoms/3 moles of Carbon)*17.9 moles of Carbon atoms=65.6

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John McCann
John McCann commented
Not sure of this answer. My way is to find number of hydrogen atoms by using the mole number of carbon atoms (17.9 moles carbon atoms) times the molar ratio. (8 moles hydrogen/3 moles carbon)


17.9 moles carbon (8 moles hydrogen/3 moles carbon)

= 47.73333333 + 17.9

= 65.6 total moles of atoms ( the repeating 3's are dropped to conform to the three digit significant figures---17.9)

I think I now see your mistake.

(11 moles of atoms/3 moles of Carbon)*17.7 moles of Carbon atoms=64.9

You wrote 17.7 moles carbon instead of 17.9. 11/3 * 17.9 gives the correct answer.
Fortis Paradise
Fortis Paradise commented
Thank you John, I edited the answer.
John McCann
John McCann commented
You're welcome.

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