gistfile1.txt

                <ul class="faqs accordion">
                <?php $cat_name = null; while (have_posts()) : the_post(); ?>

                    <?php $terms = get_the_terms($post->ID, 'categories');
                    if ($terms && !is_wp_error($terms)) : 
                        if ($cat_name != $terms[0]->name) :
                            $cat_name = $terms[0]->name; ?>
                            <h2><?php echo $cat_name; ?></h2>          
                     <?php endif; ?>

                    <?php endif; ?>

                    <li id="faq-<?php the_ID(); ?>">
                        <h3><?php the_title(); ?></h3>
                        <div class="answer"><?php the_field('answer'); ?></div>
                    </li>

                    <?php endwhile; ?>
                </ul>