Very reduced example:
\documentclass[a4paper]{article}
\usepackage{amsmath, amsthm, amssymb, mathtools}
\usepackage{siunitx}
\begin{document}
\begin{equation}\begin{aligned}
n(O2)&=\SI{\frac{0,3}{2}}{\mol}\qquad\qquad &n(Fe3O4)&=\SI{0,3}{\mol} % <- this line
\end{aligned}\end{equation}
\end{document}
However I end up with
siunitx error: "invalid-token-in-number"
n(O2)&=\SI{\frac{0,3}{2}}{\mol}
\qquad\qquad &n(Fe3O4)&=\SI{0,3}{\mol}
Any clue on what's my problem here?
Best Answer
For anyone wondering: Either use
(thanks to Skillmon) or
and input the number as \SI{3/4}{\mol}.