Question

How many moles of C8H18 contain 9.25 x 1024 molecules of C8H18

Answer 1

1 mole contains \(6.022*10^{23}\) constituent particles. If you are talking about molecules, then 1 mole contains \(6.022*10^{23}\) molecules, and the mass of that 1 mole will be simply the molecular weight of the molecule grams.

You have a different number of molecules, but want to know how many moles you have. Simply multiply your number of molecules by \(\dfrac{1 \text{ mole}}{6.022*10^{23} \text{ molecule}}\) and the result will be the number of moles.