Exclusive Category

I copied this code to list me down the latest 30 Posts with excerpts.
My problem is how can I make it that it shows only category 2 and not all Posts in the category.
I hope someone can help, as im not very php inspired :ü

<?php $recent_query = new WP_Query(); ?>
<?php $recent_query->query('showposts=30'); $ids = array(); ?>

<?php while($recent_query->have_posts()) : $recent_query->the_post();
 $ids[] = get_the_ID();
?>

            <a href="<?php the_permalink(); ?>">
            <?php the_title(); ?>

            </a> <?php the_excerpt(); ?>

<?php endwhile; ?>