I have found that some students may lack confidence in getting a sufficient grade in Chemistry for entry into the subject and university of their choice. They can feel anxious about answering questions on topics in exams. My approach to helping is when the student hits a wall with a concept/ problem we will analyze it by going back step by step, layer by layer to diagnose the part of the student's knowledge and understanding that is weak and remedy it. When tutoring one on one I have found that this does not take long. Therefore when I teach a new topic the required previous knowledge and understanding is checked as we progress to obtain a sound understanding of the new topic.