No matter what I do, I can't get the line to position properly. align* always wants to move it. and i can't use \noalignwithin \cee, or perhaps I'm not using it properly (beginner here)? Here's a MWE:  \documentclass{article} % [10] =10pt|11pt|12pt \usepackage[fleqn]{amsmath} % standard math package 1/3 \usepackage[version=3]{mhchem} % insert chem equations \usepackage[detect-none]{siunitx} % use proper si units \usepackage{cancel} %strike out text  \begin{document}   \begin{align*}     \cee{       \cancel{\mathrm{MgCl_{2(aq)}}} + \cancel{\mathrm{H_{2}O_{(l)}}} &amp;-&gt; MgO_{(s)} + \cancel{\mathrm{2HCl_{(aq)}}}       &amp;\Delta H_r&amp;=\SI{105.037}{\kJ\per\mole} \\        Mg_{(s)} + \cancel{\mathrm{2HCl_{(aq)}}} &amp;-&gt; \cancel{\mathrm{MgCl_{2(aq)}}} + \cancel{\mathrm{H_{2(g)}}}       &amp;\Delta H_r&amp;=\SI{-447.667}{\kJ\per\mole}\\         \cancel{\mathrm{H_{2(g)}}} + 1/2O2_{(g)} &amp;-&gt; \cancel{\mathrm{H_{2}O_{(l)}}}       &amp;\Delta H_r&amp;=\SI{-285.8}{\kJ\per\mole}  \\        \rule{6cm}{1pt} \\       Mg_{(s)} + 1/2O_{(g)} &amp;-&gt; MgO_{(s)}     }   \end{align*} \end{document}
Is there a package that supports the addition or subtraction of chemical equations, perhaps with automatic tabbing and a alignment.  Whilst it is obvious I could set up tables or use mathmode's align feature, it seems so much more efficient to have a package handle the tabbing automatically, since it is rather predictable in this application.  mhchem does not seem to have such a feature...      Another advantage is you could maintain the readability of your equations and you would not have the added clutter associated with tables, especially tabs &amp;, which diminish the readability of your .tex document.  And of course, the line should be automatically inserted before the last row.
Now that I'm looking into home automation, I'm thinking about automatically cutting off the fridge power from 3am ~ 5am. Given that modern refrigerators are well insulated, it should be able to withstand 2 hours of non powered cooling.  If I proceed with this project, will I see a big reduction in my monthly electrical bill? Flag post that is already in low quality review queue - any effect? Let's say I see an answer that should not have been one and I flag it as Not An Answer (NAA). On this site I have plenty of reputation and am able to use the Low Quality (LQ) review queue and cast delete recommendation votes.  Of course raising such a flag on a still virgin post brings it to the LQ review queue, but what happens if I flag a post on the main site that is already in the respective review queue?  Is my flag simply useless in that case? I doubt it would be the same as casting a delete (recommendation) vote from the queue. And when I somehow manage to find that specific post in the review queue later, it's locked down for me, because I have already cast a flag. So was that flag without any effect?  Based on how I currently guess the system works, I proposed two alternative solutions to improve the system in my feature request . They were first part of this question, but I decided to split the question from the feature requests. shortcut for commands Figure subfigure layout with different numbers Of Half-elven and mortal life Note: I will expand this question with more specific points when I have my own internet connection and more time (we're moving in, so I'm at a friend's house).  This question is broad, involved, and to some degree subjective.  (I started out as a physics-only student, but eventually decided to add a mathematics major. I am greatly interested in mathematics; the typical curriculum required for physics students is not deep or thorough enough; mathematics is more general (that means work!); and it only requires a few more classes. Naturally, I enjoy  immensely.)  This question asks mainly of undergraduate-level study, but feel free to discuss graduate-level study if you like.  Please do not rush your answer or try to be comprehensive. I realize the StackOverflow model rewards quick answers, but I would rather wait for a thoughtful, thorough (on a point) answer than get a fast, cluttered one. (As you probably know,  produces clear, useful writing; and a properly-done comprehensive answer would take more than a reasonable amount of time and effort.) If you think an overview is necessary, that is fine.  For a question this large, I think the best thing to do is focus on a specific area in each answer.    Update: To Sklivvz, Cedric, Noldorin and everyone else: I had to run off before I could finish, but I wanted to say I knew I would regret this; I was cranky and not thinking clearly, mainly from not eating enough during the day. I am sorry for my sharp responses and for not waiting for my reaction to pass. I apologize.  Re: Curricula:   Please note that I am not asking about choosing your own curriculum in college or university. I did not explicitly say that, but several people believed that was my meaning. I will ask more specific questions later, but the main idea is how a physics student should study mathematics (on his or her own, but also by choosing courses if available) to be a competent mathematician with a view to studying physics.  I merely mentioned adding a mathematics major to illustrate my conclusion that physics student need a deeper mathematical grounding than they typically receive.   And now I have to run off again. How do I get console output in C++ with a Windows program? How many subgroups of order $n$ does $D_n$ have? How many subgroups of order $n$ does $D_n$ have?  My work:  Since subgroups of $D_n$ are either cyclic or dihedral, the subgroups of order $n$ of $D_n$ are $\left&lt; r \right&gt;$ (cyclic) and $D_{n/2}$ (dihedral). However, this works only for $n$ is even and $n\geq 2$. I don't know how to do when $n$ is odd. How would I go about evaluating this integral? $$\int_0^{\infty}\frac{\ln(x^2+1)}{x^2+1}dx.$$ What I've tried so far: I tried a semicircular integral in the positive imaginary part of the complex plane, excluding the negative real axis, but had trouble calculating the residue at $z=i$ (perhaps there is a way of doing this that I don't know of). After that didn't work, I tried a rectangular box integral from $\epsilon$ to $R$, from $R$ to $R+i/2$, from $R+i/2$ to $-S+i/2$, from $-S+i/2$ to $-S+i\epsilon$, from $-S+i\epsilon$ to $-\epsilon+i\epsilon$ and finally a semicircle around the origin, radius $\epsilon$.   Any help would be appreciated. How do I create a dynamic key to be added to a JavaScript object variable If i try to update node revision like this:  $node = node_revision_load(59); $node-&gt;set('publish_on', null); $node-&gt;save();   or simple save:  $node = node_revision_load(59); $node-&gt;save();   I have a PHP memory error, (i have 1gb allocated) How to start a new Linux distro? What does `:-` mean in a shell script I saw this in the end of an awesome shell script but I can't understand the login here because I think it's being short-handed for a longer command.  spark ${@:-`cat`}   This apears at the end of . Any ideas?  + Marks for some one who extends it into a full segment of code, even if its slower (Better for explanation) Adding dynamic graphics to an animation How to custom (split in two)? Ibidem How to use figure inside a minipage? I'm trying to include an image, and keep it centered, and prevent from wrapping from the next page.  The following code works for that:  \begin{minipage}{\textwidth}     \begin{center}         Caption for image          \includegraphics[scale=0.5]{myimage.png}      \end{center} \end{minipage}   I'd like this image to be in a figure, with a caption.  The following doesn't compile:  \begin{minipage}{\textwidth}     \begin{figure}         \includegraphics[scale=0.5]{myimage.png}         \caption{Caption for image}         \label{fig:sample_figure}     \end{figure} \end{minipage}   I get the errors:  ! LaTeX Error: Not in outer par mode. ! Undefined control sequence.   How can I fix this? INT comparison without WHERE statement The Wikipedia  has a derivation of the Klein-Gordon equation.  It gets to this step:  $$\sqrt{\textbf{p}^2 c^2 + m^2 c^4} = E$$  and inserts the QM operators to get  $$\left( \sqrt{ (-i \hbar \nabla)^2 c^2 + m^2 c^4 } \right) \psi = i\hbar\frac{\partial}{\partial t} \psi$$  The article then says     This, however, is a cumbersome expression to work with because the differential operator cannot be evaluated while under the square root sign. In addition, this equation, as it stands, is nonlocal.   To fix this, the first equation is squared instead to get  $$\textbf{p}^2 c^2 + m^2 c^4 = E^2$$  after which the QM operators are inserted and the expression is simplified to get  $$-\hbar^2 c^2 \nabla^2 \psi + m^2 c^4 \psi = -\hbar^2 \frac{\partial^2}{\partial t^2} \psi$$  A couple things I don't understand.  First, are the solutions to this differential equation not exactly the same as the solutions to the first differential equation?  Both sides of the starting equation were squared, so it seems to me that regardless of the particular form of the resulting differential equation, both of them should have the exact same set of solutions.  Secondly, why is the first differential equation cumbersome to work with?  It seems like it would in fact be easier to work with, since the operator under the square root could be expanded in terms of a Taylor series and then you have an equation that is first order in time.  And finally, can someone elaborate on what nonlocal means? The linked article on the Wikipedia page didn't entirely help me understand it. Override iTunes "media" keys (play, pause, etc) for Spotify? author not appearing in \maketitle in amsart I am new to the amsart document class. For some reasons \author (etc..) is not showing after I use \maketitle. This is my tex:  \documentclass[12pt,reqno,a4paper]{amsart}  \usepackage{amsmath} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{mathrsfs}  \usepackage{amsthm}  \usepackage{latexsym}  \usepackage{pictexwd} \usepackage{pdftricks} \usepackage{natbib} \usepackage{setspace} \usepackage{color} \usepackage[affil-it]{authblk}  \begin{document}  \title{Temptation, Asymmetric information and Committment}  \author{Mark}  \affil{University of Leicester}  \date{February 2014}  \maketitle  \begin{abstract} To be written \end{abstract}  \section{introduction}  ...  \end{document}   and this is the output:   can anybody help me out?