What is the dramatic significance of this chapter?

I think the chapter speaks to Jekyll's character. Throughout the chapter, Jekyll lies to Utterson, one of his closest and most loyal friends, which foreshadows the degree to which Hyde's evilness will gain power over the otherwise respectable Jekyll. Interestingly, Jekyll also believes he can be "rid of Hyde at any point," which later proves to be tragically false. Thus, Stevenson examines the issue of control. Jekyll's addiction to Hyde's personality proves fatal, and although he believes to be in control of the situation, he is not.