Labelling aligned equations with text

Question

I have an align environment in which the equations are numbered on the left. Can I add notes on the right (e.g. to explain where each equation comes from)?

Answer 1

% arara: pdflatex

\documentclass[leqno]{article}
\usepackage{mathtools}

\begin{document}
    \begin{align}
    x&=y &&\text{comment for equation (1)}\\
    y&=x &&\text{comment for equation (2)}
    \end{align}
\end{document}