# Horizontal Lines do not span the Table length

In this table the horizontal lines, due to the \multicolumn command, do not fill the whole table.

One solution is to put extra horizontal space, as in the line with comment.
Is there another way (less trial and error) to do that? Thank you.

\documentclass[12pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage[version=3]{mhchem}
\usepackage{siunitx,booktabs}
\begin{document}

\begin{tabular}{l|cccccc}
\toprule
& \ce{COCl2(g)} & \ce{<-->} & \ce{CO(g)} & + & \ce{Cl2(g)} \\
\midrule
inizio & 1 &  &  &  & \\ [1mm]
equilibrio &  $1 - \alpha$ &  &  $\alpha$ &  & $\alpha$ \\ [1mm]
moli totali & \multicolumn{6}{l}{$1 - \alpha + \alpha + \alpha = 1 + \alpha$} \\ [1mm]
%moli totali & \multicolumn{6}{l}{$1 - \alpha + \alpha + \alpha = 1 + \alpha\hspace{56mm}$} \\ [1mm]
frazioni molari & $\dfrac{1-\alpha}{1+\alpha}$ & & $\dfrac{\alpha}{1+\alpha}$ & & $\dfrac{\alpha}{1+\alpha}$ \\ [3mm]
pressioni parziali & $\left( \dfrac{1-\alpha}{1+\alpha}\right)P$ & & $\left( \dfrac{\alpha}{1+\alpha}\right) P$ & & $\left( \dfrac{\alpha}{1+\alpha}\right) P$ \\ [1mm]
\bottomrule
\end{tabular}

\end{document}

• Hmmm... there is a missing & in the line with inizio. Jun 8, 2017 at 15:15

You need only 6 columns, so remove one c from the column specification. Also, since all the columns 2-6 are in math mode, spare these $s by adding >{$}c<{$} in the column specification. \documentclass[12pt,a4paper]{article} \usepackage[utf8]{inputenc} \usepackage[version=3]{mhchem} \usepackage{siunitx,booktabs,array} \begin{document} \begin{tabular}{l*5{>{$}c<{$}}} \toprule & \ce{COCl2(g)} & \ce{<-->} & \ce{CO(g)} & + & \ce{Cl2(g)} \\ \midrule inizio & 1 & & & & \\ [1mm] equilibrio & 1 - \alpha & & \alpha & & \alpha \\ [1mm] moli totali & \multicolumn{5}{l}{$1-\alpha+\alpha+\alpha = 1+\alpha\$} \\ [1mm]

• Yes... or a c more in the tabular. ;-) Jun 8, 2017 at 15:33