a) Research and list the boiling point of the first 10 alkanes.
b) Explain the trend you observe in their boiling points.
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.
Can you put b) in simple terms
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.
a) Here are the boiling points of the first 10 alkanes:
1. Methane (CH4): -161.5°C
2. Ethane (C2H6): -88.6°C
3. Propane (C3H8): -42.1°C
4. Butane (C4H10): -0.5°C
5. Pentane (C5H12): 36.1°C
6. Hexane (C6H14): 68.7°C
7. Heptane (C7H16): 98.4°C
8. Octane (C8H18): 125.7°C
9. Nonane (C9H20): 151.1°C
10. Decane (C10H22): 174.0°C
b) The trend observed in the boiling points of alkanes is that they generally increase as the number of carbon atoms in the molecule increases. This trend can be explained by two main factors:
1. Molecular weight: As the number of carbon atoms increases, so does the molecular weight of the alkane. Larger molecules have stronger intermolecular forces, which require more energy to overcome, resulting in higher boiling points.
2. Surface area: With an increasing number of carbon atoms, the surface area of the molecule increases. This leads to a larger area of contact between molecules, which enhances the strength of the intermolecular forces (such as London dispersion forces) acting between the alkane molecules. The stronger these forces, the higher the boiling point.
It is important to note that there may be exceptions or anomalies in the boiling points of certain alkanes due to factors like branching or isomerism, which can affect the intermolecular forces and therefore the boiling point. However, in general, the boiling points of alkanes increase with increasing carbon chain length.
a) To research and list the boiling point of the first 10 alkanes, we need to gather information on their boiling points. Alkanes are a family of organic compounds with the general formula CnH2n+2, where n represents the number of carbon atoms in the molecule. Here are the boiling points of the first 10 alkanes:
1. Methane (CH4): -161.6°C
2. Ethane (C2H6): -88.6°C
3. Propane (C3H8): -42.1°C
4. Butane (C4H10): -0.5°C
5. Pentane (C5H12): 36.1°C
6. Hexane (C6H14): 69.0°C
7. Heptane (C7H16): 98.4°C
8. Octane (C8H18): 125.7°C
9. Nonane (C9H20): 151.6°C
10. Decane (C10H22): 174.1°C
b) When observing the trend in the boiling points of the first 10 alkanes, we can notice the following pattern:
1. The boiling points generally increase as the number of carbon atoms in the alkane increases.
2. The increase in boiling point is due to the increased number of electrons and London dispersion forces (also called Van der Waals forces) that result in stronger intermolecular forces between the molecules.
3. London dispersion forces occur due to temporary imbalances in the electron distribution, resulting in a temporary dipole within a molecule. These temporary dipoles induce other temporary dipoles in neighboring molecules, leading to attractions between the molecules.
4. As the size and complexity of the alkane molecules increase, the molecular weight and the ability to exhibit stronger London dispersion forces also increase. This results in higher boiling points.
5. Methane, the smallest alkane, has the lowest boiling point because it has the weakest London dispersion forces.
6. Decane, the largest alkane, has the highest boiling point due to its greater number of carbon atoms and a higher molecular weight, resulting in stronger London dispersion forces.
In conclusion, the boiling points of alkanes increase as the number of carbon atoms increases due to the increase in molecular size, molecular weight, and the strength of London dispersion forces.