Which of the following is an alkene?

**The reasoning** An **alkene** is a hydrocarbon with at least one **carbon-carbon double bond (C=C)**. Alkenes follow the general formula **CₙH₂ₙ**. Let's check each option: - **A) CH₄** → C₁H₄ = C₁H₂(₁) ✓ But this is **methane**, an alkane (single bonds only) - **B) C₂H₆** → C₂H₂(₂)+₂ = C₂H₆ — This fits **alkanes (CₙH₂ₙ₊₂)**, so it's ethane - **C) C₃H₆** → C₃H₂(₃) = C₃H₆ ✓ This fits **CₙH₂ₙ** perfectly! This is **propene**, an alkene - **D) C₂H₂** → C₂H₂(₂)−₂ = C₂H₂ — This fits **alkynes (CₙH₂ₙ₋₂)**, so it's ethyne (acetylene) with a triple bond **Why the wrong options tempt you** Without knowing the formulas, they all look like random hydrocarbon combinations. **CH₄** and **C₂H₆** are common alkanes you've heard of. **C₂H₂** looks simple and might seem like it has fewer hydrogens because of unsaturation—but it's a *triple* bond (alkyne), not a double bond. **Quick takeaway** Alkenes = **CₙH₂ₙ** (equal number ratio: C₃H₆, C₄H₈). Just count: if hydrogen = 2 × carbon, you've found your alkene!