A Level Chemistry OCR Practice Exam

What does the general formula for alkanes represent?

1. The simplest formula of hydrocarbons

2. The molecular structure of all organic compounds

3. The composition of terpenes

4. The general formula for alkenes

The correct answer is: The simplest formula of hydrocarbons

The choice indicating that the general formula for alkanes represents the simplest formula of hydrocarbons is accurate because the formula for alkanes is CnH2n+2. This reflects that alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms and are fully saturated with hydrogen atoms. Each carbon atom can bond with two hydrogen atoms for every carbon-carbon bond it forms. Alkanes serve as a foundational category within organic chemistry, characterized by their lack of functional groups other than carbon and hydrogen. This formula applies universally to all alkanes, providing a clear and simplified way to describe their molecular formula based solely on the number of carbon atoms present. In contrast, the other options touch upon different or broader concepts. The molecular structure of all organic compounds, for example, would encompass a wide variety of compounds, including those with functional groups beyond just alkanes. The composition of terpenes specifically relates to a diverse class of organic compounds typically derived from plants, not strictly alkanes. Lastly, the general formula for alkenes applies to another group of hydrocarbons characterized by at least one carbon-carbon double bond, which is distinctly different from the single-bond structure of alkanes. Thus, the