Many reactions are invoked/sped up by presence of certain chemical substance. This is called catalysis.
As far as I know, catalyst is then written above the arrow of the reaction. The same is also used when reaction requires certain temperature or pressure. How do I write this properly using Tex?
So far, was using this approach:
$$\ce{2NaHCO3 →300°C→ Na2CO3 + H2O + CO2}$$
I don't really like it.
Use [...] right after the arrow. Use it again if you want to add more text below the arrow.
$$\ce{Pb ->[\rm magic][\Delta] Au}$$
If you want to include chemical formulas you have to include them in [\ce{...}]$$\ce{Pb ->[\mathrm{magic}~\ce{H2O}][\Delta] Au}$$
Use T[...] right after the arrow to add descriptive text. If you want to add something below the equation, this will also be set as text, you have to escape with $...$ again if you want to add math or chemistry $\ce{...}$.
$$\ce{Pb ->T[magic water with the eye of Newt][$\Delta$] Au}$$
\rm, while here this does not really matter, but in a LaTeX document this might destroy your markup. Use {\rmfamily ...}, \textrm{}, \mathrm{} instead.
$\endgroup$
→to set the arrows. There are a variety of possibilities to do that with mhchem which is implemented in MathJax. For example $\ce{->}$$\ce{->}$; $\ce{<->}$$\ce{<->}$; $\ce{<=>}$$\ce{<=>}$, $\ce{<<=>}$$\ce{<<=>}$... Use the sandbox to experiment :D $\endgroup$