Setting tabular width

Question

I'm using a tabular within multicols and would like to make a table extend its second column right to the edge of the column within multicols, so the column is pushed over but the text is still left justified. The code I'm trying to use this:

\documentclass[11pt, a4paper]{article}
\usepackage{tikz}
\usepackage{a4wide}
\usepackage{multicol}
\usepackage{amsmath}

\begin{document}
\begin{multicols*}{2}
\section{Notation}
\begin{tabular}{l l}
$Q_r$ & Heat energy rejected \\
$Q_s$ & Heat energy supplied \\
$R$ & Real gas constant for fluid \\
\end{tabular}
\end{multicols*}
\end{document}

Answer 1

Assuming you want the first column 4cm wide, flush with the left margin, and the second column to take all the available space, flush with the right margin, then

\usepackage{tabularx}

in the preamble and

\noindent\begin{tabularx}{@{}p{4cm}X@{}}
$Q_r$ & Heat energy rejected \\
$Q_s$ & Heat energy supplied \\
$R$ & Real gas constant for fluid \\
\end{tabularx}

should do.

Note that a4wide is an obsolete package that shouldn't be used any more (see texdoc l2tabuen).

Answer 2

If I understand correctly what you want, you can do this with LaTeX's tabular* environment.

\documentclass[11pt, a4paper]{article}

\usepackage{booktabs}
\usepackage{multicol}

\begin{document}
\begin{multicols*}{2}
\noindent
\begin{tabular*}{\columnwidth}{ll}
  \toprule
  $Q_r$ & Heat energy rejected
\\$Q_s$ & Heat energy supplied
\\$R$   & Real gas constant for fluid
\\\bottomrule
\end{tabular*}
\end{multicols*}
\end{document}

Looking at what you're trying to do, it looks you're trying to make some kind of glossary. Are you sure you don't want to use a dedicated package for this? For example the glossaries package?