Final answer:
Chapter 6 covers Chemical Composition, focusing on substances in chemical reactions, heat exchange, reaction volumes, and related calculations.
Step-by-step explanation:
The topic of Chapter 6 is Chemical Composition. This chapter deals with the amounts of substances involved in chemical reactions, the heat exchanged during these reactions, solution volumes that react with each other, and related calculations. These topics are unified because the calculations for these different aspects share similar forms, including those for density, molar mass, and the use of the Avogadro constant.