# What is the empirical formula of C5H10?

The empirical formula of ${C}_{5} {H}_{10}$ is $C {H}_{2}$
The empirical formula is the simplest whole number ratio that describes constituent atoms in a species. ${C}_{5} {H}_{10}$ of course can be reduced to $C {H}_{2}$.
The molecular formula is always a multiple of the empirical formula (the multiple might be 1). A very useful parameter with molecular formulae is the "degree of unsaturation" concept. An alkane has the general formula ${C}_{n} {H}_{2 n + 2}$ (this could be the same as the empirical formula!). If presented with a molecular formula ${C}_{n} {H}_{2 n}$ we would say that this molecule has ${1}^{\circ}$ of unsaturation. A degree of unsaturation has a double bond ($C = C$, $C = O$, $C = N$) OR a ring to account for the absence of the 2 hydrogens. Simple acetylenes have 2 degrees of unsaturation. Why?