I need to clarify something about writing a novel?

You've got a whole lot more words to play with in any way that serves your novel. Maybe it's longer descriptions. Maybe it's deeper character development. Maybe it's more complex plot and the addition of subplots. Maybe it's lyrical prose.

Whatever comprises your total word count is fine--so long as it either illuminates character or develops plot. If it doesn't do much of either, cut it to the bone. Words that give details on setting or evoke a mood belong in there, but as briefly as required to do the job.

No, it's not expected. You'll find novel writers with sparse prose and short story writers with rich prose.

With a novel you have more space to play with, but that's not to say that you need to fill that space with details. Bottom line, as always, is to do what works and what suits your story. A lot of novice writers believe that they have to start out their novel with purple prose: Pages of rich and detailed description, filled with "big" words (many of which I suspect they found in a thesaurus). It gets pretty tedious to read.

And on the other hand, there's such a thing as too sparse, where the reader is left floundering about with no detail or setting to ground him.

What you don't want to do, however, is to write detail as space-fillers, that's usually when your readers' eyes start to glaze over. A novel is not just a longer short story.

Remember, everything can be changed. In my opinion, first drafts are hard enough to get down as it is, so why not write them as they come to you naturally? And then go back and alter what needs to be altered. Most writers need to cut words afterwards, I'm the other way round. Once you start writing and get feedback, you should get a pretty good idea of where your strengths and weaknesses lie, and what kind of writer you are. Then you of course work on those weaknesses.

All the best with your novel.

I wouldn't really worry so long as it's written well. Like MsBittner pointed out, there are many reasons why you might be spending more time on descriptions with a novel. In general though, it's easy to overdo descriptions.

If you're not sure about the amount, then I'd suggest getting some opinions on your work. If you have to cut stuff out, that's okay. The editing process often involves trimming stuff down. Publishers/editors often ask authors to cut certain stuff out. Best selling authors do it too. Honestly, you probably do have to cut stuff out somewhere. Good writers are usually good editors, and good editors look for ways to keep things concise.