Chemistry is an experimental science. The laws and theories that you learn in the various chemistry courses are based upon research. To truly understand chemistry, it is necessary that you appreciate how research is carried out.
Many chemistry majors go on to careers that involve or are based on research. Participation in research allows you to decide whether you enjoy research and thus to make a more informed career choice. Strong, professional relationships with research mentors provide you with important insights into career choices, and enable faculty members to write stronger recommendation letters for graduate and professional schools.
Research may also qualify you for certain scholarship and award competitions, consideration for publication of research results in scientific journals, and presentation of research results at scientific meetings. Any or all of these are impressive on applications for graduate/professional schools or employment.