\documentclass{article}

\usepackage{fancyhdr}
\usepackage[margin=1in]{geometry}
\pagestyle{fancy}

\renewcommand{\headrulewidth}{0.5pt}
\renewcommand{\footrulewidth}{0pt}
\lhead{Josiah\\ Carberry}
\chead{\roman{page}}
\rhead{Homework \# 4}

\lfoot{\LaTeX{} Lectures}
\cfoot{}
\rfoot{\today}

\newcommand{\problem}[1]{\subsection*{Problem #1:}}


\usepackage{siunitx}
\usepackage{mhchem}

\begin{document}

\begin{abstract}
	This is pretty abstract, eh?
\end{abstract}

\problem{12.5}
fdfssaf
\si{\joule\per\second}

\problem{12.8}
\ce{H_2O <=>> OH- + H+}

%The book \cite{hp1}.

%\bibliographystyle{plain}
%\bibliography{references.bib}
\end{document}