How to cite different chapters of a book in the same paragraph?
If the chapters are part of a unified work (e.g., a textbook or monograph), then it's appropriate to use one citation, and to say the chapter in the text:


  Here's what I'm doing. Chapter 2 of (Trout, 1946) presents an interesting fact. I
  then fit the interesting model, described in Chapter 8 of (Trout, 1946).
  
  References: Trout, Kilgore. (1946). Ice-9 and its Applications. Ilium,
  NY: Slaughterhouse Press.


I'm not quite sure of where APA puts the parentheses; my point is about handling chapters as prose.

On the other hand, if the chapters are separate pieces of a collection (e.g., contributed texts in a "recent results in..." book), then each should have an independent entry in the bibliography.