# Formatting problem with \tag markup

I tried adding the following markup to an answer.

$$\ce{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)}\tag{Open Circuit voltage 1.1018 V}$$

$$\ce{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)\tag{Open Circuit voltage 1.1018 V}}$$

both of which which render as

$$\ce{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)}\tag{Open Circuit voltage 1.1018 V}$$

Why does it run off the right side of the view?

I finally switched to

$$\quad\quad\quad\quad\ce{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)}\quad\quad\quad\text{(Open Circuit voltage 1.1018 V)}$$

which renders as

$$\quad\quad\quad\quad\ce{Zn(s) + Cu^{2+}(aq) → Zn^{2+}(aq) + Cu(s)}\quad\quad\quad\text{(Open Circuit voltage 1.1018 V)}$$

There must be some better way to do this.

• This issue has explained by the developer of MathJax in a related post on Meta.Math.SE. Also, I've replaced mhchem with mathjax as this does not seem to be an mhchem issue. Commented Sep 23, 2018 at 9:56
• @GaurangTandon - Not sure how much mhchem does and what mathjax does. I edited question to note that same problem occurs if \tag{} part is in or out of \ce{}.
– MaxW
Commented Sep 23, 2018 at 14:52

\begin{align} \ce{Zn (s) + Cu^2+ (aq) &-> Zn^2+ (aq) + Cu (s)} & \text{Open Circuit voltage} &: \pu{1.1018 V} \tag{1}\label{opencircuitvoltage} \end{align}
\begin{align} \ce{Zn (s) + Cu^2+ (aq) &-> Zn^2+ (aq) + Cu (s)} & \text{Open Circuit voltage} &: \pu{1.1018 V} \tag{1}\label{opencircuitvoltage} \end{align}

In the above example you can then refer to the tag via the label like \ref{opencircuitvoltage}, \eqref{opencircuitvoltage} to produce \ref{opencircuitvoltage}, \eqref{opencircuitvoltage}.