The compounds made up of only carbon and hydrogen are called?

Analysis

The question asks for the specific classification of chemical compounds that consist exclusively of two elements: carbon and hydrogen.

Concept Explanation

In organic chemistry, compounds are classified based on their elemental composition.

• Hydrocarbons are the simplest organic compounds. As the name suggests ("hydro" for hydrogen and "carbon" for carbon), they are molecules that contain only carbon and hydrogen atoms bonded together.
• They form the foundation of organic chemistry and are categorized into groups like alkanes, alkenes, alkynes, and aromatics (like benzene).
• Other options like "Carbon compounds" is a broad term that includes things like carbon dioxide ($CO_2$) or carbonates, which contain oxygen and are not hydrocarbons.

Step-by-Step Solution

1. Identify the components: The question specifies "only carbon and hydrogen."
2. Evaluate Option A: "Carbon compounds" is too general. It includes substances like $CaCO_3$ (calcium carbonate), which contains oxygen.
3. Evaluate Option B: "Hydrocarbons" are defined by IUPAC as compounds consisting entirely of hydrogen and carbon. This matches the criteria perfectly.
4. Evaluate Option C: "Atoms" are the basic building blocks of matter, not compounds.
5. Evaluate Option D: "Carbon hydrolysis" is a chemical reaction involving water, not a classification of a compound.

Conclusion

Since the definition of a hydrocarbon is a compound containing only carbon and hydrogen, Option B is the correct classification.

Exam Tip

Whenever you see the prefix "Hydro-" in chemistry, think of hydrogen. When you see "-carbon," think of carbon. Combining them gives you the exact definition! This is a common "free mark" question in JAMB, so ensure you remember that hydrocarbons are the parent class of all organic molecules.