Compile two A5 pages on one A4 page

The following uses, as also suggested by DG', the pgfpages package to do the 1x2 A5 on A4 layout, but automatically duplicates the content of each A5 page at shipout time, so that you end up with two identical A5 copies on each A4 page.

It also works with multi-page documents.

\documentclass[a5paper,12pt,norsk]{article}
\usepackage[utf8]{inputenc}
\usepackage{babel,fouriernc,parskip,booktabs,array}
\usepackage[margin=1cm,landscape]{geometry}
\usepackage{enumitem}

\usepackage{pgfpages}                                 % <— load the package
  \pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm] % <— set options

\usepackage{atbegshi}
  % duplicate the content at shipout time
  \AtBeginShipout{
    \pgfpagesshipoutlogicalpage{1}\copy\AtBeginShipoutBox
    \pgfpagesshipoutlogicalpage{2}\box\AtBeginShipoutBox
    \pgfshipoutphysicalpage
  }

\usepackage{blindtext}


\setlist{nolistsep}
\renewcommand\labelitemi{--}

\begin{document}
\thispagestyle{empty}
{\Large <<Jeg kan>> om kjemi}

\vspace{1em}
\begin{center}
\begin{tabular}{p{0.7\textwidth} |>{\centering}p{0.1\textwidth}| >{\centering}p{0.1\textwidth}}
    \toprule
    \textbf{Spørsmål} & \textbf{ja} & \textbf{nei} \tabularnewline
    \hline
    \dots some text & & \tabularnewline
    \bottomrule
\end{tabular}
\end{center}

% To demonstrate that it also works with multiple pages
\newpage

\blindtext

\end{document}

Remark: If your a5 pages are portrait, then the setup is:

\documentclass[a5paper]{article}
...
\usepackage[margin=1cm,portrait]{geometry}
...
\usepackage{pgfpages}
\pgfpagesuselayout{2 on 1}[a4paper,landscape,border shrink=5mm]
...

UPDATE: Added code to duplicate the page. But you should use @Daniels solution as it is much more versatile.

You could use pgfpages:

\documentclass[a5paper,12pt,norsk]{article}
\usepackage[utf8]{inputenc}
\usepackage{babel,fouriernc,parskip,booktabs,array}
\usepackage[margin=1cm,landscape]{geometry}

\usepackage{forloop}                                  % <-- needed to duplicate page 
\usepackage{pgfpages}                                 % <-- load the package
\pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm] % <-- set options

\usepackage{enumitem}
\setlist{nolistsep}
\renewcommand\labelitemi{--}

\begin{document}

\newcounter{counter}
\forloop{counter}{0}{\value{counter} < 2}{% <-- Print the page twice
    \thispagestyle{empty}
    {\Large <<Jeg kan>> om kjemi}
    \vspace{1em}
    \begin{center}
    \begin{tabular}{p{0.7\textwidth} |>{\centering}p{0.1\textwidth}| >{\centering}p{0.1\textwidth}}
        \toprule
        \textbf{Spørsmål} & \textbf{ja} & \textbf{nei} \tabularnewline
        \hline
        \dots some text & & \tabularnewline
        \bottomrule
    \end{tabular}
    \end{center}
    \clearpage
}
\end{document}

This results in: