Alright, so, as some other people have already said, most (is it YA?) books are between 60k (250 pages, paperback) to 100k (around 3 hundred to four hundred pages, paperback). But there are exceptions, like Twilight (120k or 400 some odd pages) and some others. So really, I would shoot somewhere in there.
As for chapters, what I do is take my total word count goal, and divide it by how many chapters I want. I tend to aim towards odd numbers, so say I'm thinking 23 chapters out of 86 thousand words. You can always fudge that though, which I do, frequently. If it gets published, they may want to even out the chapters, but for now I don't think it matters.
I believe you should just write, and enjoy it, and don't stress about the perfect amount of words in a chapter. It doesn't really matter, but it's best to *try* to keep them close to the same size. (I normally shoot for 4500 per chapter, but then mostly they're 5k, and some are 6k, so I don't think it's important. :)
Anywho, hope I helped! =)