Hydrocarbons are organic compounds composed exclusively of:
- Carbon and oxygen
- Carbon and hydrogen
- Carbon and nitrogen
- Hydrogen and nitrogen
Show answer and solution
Correct answer: B. Carbon and hydrogen
By definition, hydrocarbons contain **only** carbon and hydrogen atoms. Adding oxygen, nitrogen, halogens, etc. produces other functional-group families (alcohols, amines, halides).
Three main classes:
- **Alkanes**: only single C-C bonds, $C_nH_{2n+2}$.
- **Alkenes**: contain at least one C=C double bond, $C_nH_{2n}$.
- **Alkynes**: contain at least one C≡C triple bond, $C_nH_{2n-2}$.
Aromatic hydrocarbons (e.g. benzene) are a special case.