Which of the following molecules contains a triple bond?

• A. C2H4
• B. C3H6
• C. C2H2
• D. C2H6

Answer: (C)

Verified step by step guidance

1. Step 1: Understand what a triple bond is — it is a type of covalent bond where three pairs of electrons are shared between two atoms, commonly found in alkynes.
2. Step 2: Analyze the molecular formulas given and identify the type of hydrocarbons they represent. For example, C2H4 is ethene (an alkene), C3H6 is propene or cyclopropane (alkene or cycloalkane), C2H2 is ethyne (an alkyne), and C2H6 is ethane (an alkane).
3. Step 3: Recall the general formulas for different types of hydrocarbons: alkanes (C_nH_{2n+2}), alkenes (C_nH_{2n}), and alkynes (C_nH_{2n-2}). Use these to determine which molecule corresponds to an alkyne, which contains a triple bond.
4. Step 4: Match each formula to its hydrocarbon type using the formulas: C2H4 fits C_nH_{2n} (alkene), C3H6 fits C_nH_{2n} (alkene), C2H2 fits C_nH_{2n-2} (alkyne), and C2H6 fits C_nH_{2n+2} (alkane).
5. Step 5: Conclude that the molecule with the formula C2H2 is the one that contains a triple bond, as it fits the alkyne formula and is known as ethyne.