If all your <h2> are class="chapno", you don't need the class at all to style them.
It might be interesting, however, to have the possibility of styling the word "Chapter" and the chapter number (and the title, if any) separately, with something like this:
Code:
<h2><span class="name">Chapter</span> <span class="num">1</span><br/>
<span class="title">An Unexpected Party</span></h2>