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Reactions and Periodicity
Reactions will always occur in the free-response section of the AP Exam.AP Exam Format
Beginning with the 2007 AP exam, the treatment of chemical reactions was changed from
previous years. In the past, the free-response questions concerning chemical reactions have
simply involved the formulas of the reactants and products chosen from a series of reac-
tions. You were not expected to write balanced chemical equations. However, under the
current AP Chemistry exam format you no longer will be able to choose from a list of reac-
tions. You will be expected to write a balanced chemical equation for every reaction given
and answer one or more questions about each reaction. If the reaction occurs in aqueous
solution, you will have to write the net ionic equation for the process. For the reactions
question of the AP exam, you will be expected not only to balance the equation, but to
have an understanding of why the reaction occurs. The reactions and concepts described
may also appear in other parts of the AP exam, such as the multiple-choice sections. Again,
you will need to have an understanding of why a particular reaction occurs. As you study
this chapter, pay particular attention to the explanations that accompany the reactions and
equations. You will be expected to demonstrate your understanding on the AP exam.IN THIS CHAPTER
Summary:Chemistry is the world of chemical reactions. Chemical reactions
power our society, our environment, and our bodies. Some chemical species
calledreactantsget converted into different substances called products.
During this process there are energy changes that take place. It takes energy
to break old bonds. Energy is released when new bonds are formed. Does it
take more energy to break the bonds than is released in the formation of the
new bonds? If so, energy will have to be constantly supplied to convert the
reactants into products. This type of reaction is said to be endothermic,CHAPTER
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