International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following statements about alkanes is true?

1. They are all cyclic compounds

2. They have single bonds between carbon atoms

3. They have at least one double bond

4. They contain functional groups

The correct answer is: They have single bonds between carbon atoms

The statement that alkanes have single bonds between carbon atoms is correct because alkanes are defined as saturated hydrocarbons. This means they contain only single bonds between carbon atoms, which gives them a general formula of CnH2n+2, where n represents the number of carbon atoms. The presence of only single bonds ensures that each carbon atom is bonded to the maximum number of hydrogen atoms possible, leading to the stability characteristic of alkanes. Cyclic compounds and functional groups relate more to different classes of hydrocarbons or organic compounds, while the presence of double bonds is a feature of alkenes, not alkanes. Thus, the hallmark of alkanes is indeed their single bonds, which is why this statement is considered true.