Question

Which of the following alkanes is used for road surfacing?

• A. C$_{15}$H$_{32}$ to C$_{19}$H$_{40}$
• B. C$_{10}$H$_{22}$ to C$_{12}$H$_{26}$
• C. C$_{36}$H$_{74}$ and above
• D. C$_{20}$H$_{42}$ to C$_{24}$H$_{50}$

Answer 1

Answer: (D)

C$_{20}$H$_{42}$ to C$_{24}$H$_{50}$

Answer 2

Road surfacing employs bitumen, which is derived from heavy oil fractions containing long‐chain alkanes. Lighter alkanes (such as C₁₀–C₁₂ and C₁₅–C₁₉) are too volatile for this use, while extremely heavy ones (C₃₆H₇₄ and above) are often too waxy. The moderately heavy fraction, typically in the range C₂₀H₄₂ to C₂₄H₅₀, provides the proper viscosity and adhesive properties.