# How do I find the amount of moles from the amount of units?

The problem:

Find out the amount of moles of a certain substance knowing that the amount of units of said substance is $$\pu{1.8E23}$$. I have to find how many moles of carbon, hydrogen, and oxygen that amounts to. The number $$\pu{1.8E23}$$ was calculated in a previous question where I was asked to find the amount of units in $$n(\ce{C6H12O6}) = \pu{0.3 mol}$$.

\begin{align} &\ce{C}: \pu{1.1E24} \\ &\ce{H}: \pu{2.2E24} \\ &\ce{O}: \pu{1.1E24} \end{align}

Try 1: \begin{align} m(\ce{C6H12O6}) &= M(\ce{C6H12O6}) \cdot n(\ce{C6H12O6}) \\ &= (\pu{180.156 g mol-1})(\pu{0.3 mol}) = \pu{54.0468 g} \end{align} so that $$$$n(\ce{C}) = \frac{\pu{54.0468 g}}{(\pu{12.01 Da})(\pu{1.6603E-24 g/Da})} \approx \pu{2.71E24}$$$$ Which is not the right answer. The right answer for carbon is $$\ce{C}: \pu{1.1E24}$$.

Try 2: $$$$n(\ce{C}) = \left(\frac{\pu{1.8E23}}{\pu{1.6603E-24 g/Da}}\right) (\pu{12.01 Da}) \approx \pu{1.30E48}$$$$ Which is not the right answer either.

Each molecule of glucose has 6 carbon atoms. Hence a given number of molecules of glucose would have 6 times the carbon atoms. Since you have $$\pu{1.8E23}$$ atoms of glucose, the number of atoms of carbon would be this number multiplied by 6 which gives us $$\pu{1.08E24}$$ atoms.