a) Research and list the boiling point of the first 10 alkanes.

Question

b) Explain the trend you observe in their boiling points.

Answer 1

a) The boiling points of the first 10 alkanes are as follows:

- Methane (CH₄): -161.6 °C
- Ethane (C₂H₆): -88.6 °C
- Propane (C₃H₈): -42.1 °C
- Butane (C₄H₁₀): -0.5 °C
- Pentane (C₅H₁₂): 36.0 °C
- Hexane (C₆H₁₄): 68.7 °C
- Heptane (C₇H₁₆): 98.4 °C
- Octane (C₈H₁₈): 125.6 °C
- Nonane (C₉H₂₀): 150.8 °C
- Decane (C₁₀H₂₂): 174.0 °C

b) The trend observed in the boiling points of alkanes is that they increase with increasing molecular size or number of carbon atoms. This can be attributed to the increase in London dispersion forces (also known as van der Waals forces) between the molecules as the size of the molecule increases.

London dispersion forces are weak intermolecular forces that arise from temporary fluctuations in electron distribution. They become stronger as the surface area of the molecule increases. The larger alkanes have more surface area available for these weak forces to act on, leading to stronger intermolecular attractions and thus higher boiling points.

Additionally, with increased molecular size, the number of electrons and protons also increases. This increases the overall strength of the London dispersion forces, further contributing to the higher boiling points of larger alkanes.

Therefore, the boiling points of alkanes generally increase as the number of carbon atoms in the molecule increases.

Answer 2

Can you put b) in simple terms

Answer 3

Sure! In simple terms, the boiling point of alkanes increases as the number of carbon atoms in the molecule increases. This is because bigger alkanes have more surface area and more electrons and protons, which results in stronger forces that hold the molecules together. These forces are responsible for keeping the molecules from easily separating into a gas, so when the boiling point is higher, it means the substance takes more heat to turn into a gas.