In a single-displacement reaction, what happens?

• A. Two compounds exchange anions
• B. One element or radical replaces another element or radical
• C. A compound breaks into simpler substances
• D. A hydrocarbon reacts with oxygen

Answer: (B)

In a single-displacement reaction, one element takes the place of another in a compound, forming a new element and a new compound. This happens because the more reactive element tends to lose electrons and push the less reactive element out of the compound, a redox process where the active element is oxidized and the displaced element is reduced. This is exactly what the description “one element or radical replaces another element or radical” captures. The other options describe different processes: exchanging anions is a double displacement, a compound breaking apart is decomposition, and a hydrocarbon reacting with oxygen is combustion.