# How to typeset Hess' Cycle in tikz-cd?

I want something like this:

A        B
ΔH        \       /
(-397*2)      \     /
C

Where the arrow points from A to C, and from B to C.

How can I do this with tikz-cd?

I now know how to do this using aliases, how can I do this without alias

• While I know Hess' law I must confess I don't really understand what the diagram should look like in the end... a picture similar to the one in the link I provided is doable with chemfig and probably also with tikz-cd – cgnieder Aug 27 '14 at 15:32
• I don't see the link you provided? – 11Kilobytes Aug 27 '14 at 16:35
• Click on the words »Hess' law« in my previous comment :) – cgnieder Aug 27 '14 at 19:01

Your question is quite vague which is why I was hesitating to post an answer. But I suspect (unless you're actually using A, B, and C as compounds) the answer will be “I'd use chemfig”, anyway...

Chemical schemes can be typeset fairly easy with chemfig once you understand how the \arrow command works.

The siunitx package can be used for numbers with units, the chemmacros package provides a lot of additional goodies for chemists. (For example the \Enthalpy macro).

\documentclass{article}
\usepackage{chemfig}% for the scheme mechanism, uses TikZ
\usepackage{chemmacros}% for the \ch command, also loads `siunitx'
\begin{document}

\schemestart
\ch{C\sld{} + 2 H2O\gas}
\arrow{->[\SI{90.1}{\kilo\joule}]}[,1.5]
\ch{CO2\gas{} + 2 H2\gas}
\arrow{<-[][*{0.north west}\SI{-393.5}{\kilo\joule}]}[-125,2]
\ch{C\sld{} + 2 H2\gas{} + O2\gas}
\arrow(@c3--@c1){->[][*{0.north east}\SI{-483.6}{\kilo\joule} ]}
\schemestop

\end{document}

• Do you know how to add arrows from first line to second from specific species? I'd like to have one arrow to link the two "C(s)", one arrow to link "H_2O" to "H_2" and one arrow to link the whole equation below to the right part of equation above "CO_2 + 2 H_2". – Julien Faure Nov 7 '19 at 9:10