# How many carbon atoms are in 2.12 mol of propane? How many hydrogen atoms are in 2.12 mol of propane?

Feb 29, 2016

We answer in terms of $\text{Avogadro's Number}$, ${N}_{A}$ $=$ $6.022 \times {10}^{23}$.
${N}_{A}$ is simply another collective number like a dozen, or a gross, or a score. Admittedly, ${N}_{A}$ is a VERY large number. We have $2.12 \times {N}_{A}$ molecules of propane, ${H}_{3} C - C {H}_{2} - C {H}_{3}$.
If we have this number of propane molecules, there are clearly $3 \times 2.12 \times {N}_{A}$ $\text{carbon atoms}$, and $8 \times 2.12 \times {N}_{A}$ $\text{hydrogen atoms}$. It would be worth your while to get your head around these quantities; they are simply NUMBERS.
${N}_{A}$ has the property that such a number of ""^1H ATOMS a mass of $1$ $g$, or such a number of ""^12C atoms has a mass of $12$ $g$. ${N}_{A}$ is thus the link between atoms and molecules, about which we can only theorize, and the macro world or $g$ and $k g$ and $\text{litres}$, that which we can measure in the laboratory by mass or by volume. What is the mass of your quantity of propane molecules?