Final answer:
The chemical reaction with general notation AB → A + B is a decomposition reaction, where a single compound breaks down into simpler substances (b).
Step-by-step explanation:
A chemical reaction with the general formula AB → A + B is best classified as a decomposition reaction. A decomposition reaction is characterized by a single compound breaking down into two or more simpler substances.
This is in contrast to a synthesis (or combination) reaction, where multiple reactants combine to form a single product (A + B → AB), a single replacement reaction, where one element replaces a similar one in a compound (A + BC → AC + B), and a double replacement reaction, where parts of two compounds exchange places to form two new compounds (AB + CD → AC + BD).