You can. You can give it whatever class you like within the loop. The loop is simply the PHP which produces the HTML markup for each post, so you can wrap it in whatever HTML tags you like. You mentioned in your 2nd post though that you wanted to select posts individually, and using the WordPress post_class() function gives each post a unique class you can use to target it with.
Just a thought, but have you ever considered investing in Chris’s book Digging into WordPress? This is all explained very thoroughly in there. I’d highly recommend it.