How many moles of molecules are in 35 g of octane, #C_8H_18#?

1 Answer
Apr 11, 2017

There are 0.307 moles of molecules in 35 g of octane.


You start by finding the molar mass of octane, #C_8H_18#

This is 114 grams, because there are eight moles of carbon atoms and eighteen moles of hydrogen atoms in each mole of octane molecules.

So, we total up 8 x 12 (for the carbon) and 18 x 1 (for the hydrogen).

Next, take the given mass, and divide by this molar mass:

# 35 g -: 114 g/"mol" = 0.307 "mol"#

That's it! This answer is the number of moles of octane molecules contained in the 35 grams of the compound.