The boiling point of oxygen (O₂) under standard atmospheric conditions, which are defined as a pressure of 1 atmosphere (atm) or 101.325 kilopascals (kPa), is 90.188 K (-182.963°C or -297.333°F). This value is a fixed point in the International Temperature Scale of 1990 (ITS-90) and is used as a reference point for temperature measurements.
Understanding the Boiling Point of Oxygen
The boiling point of a substance is a physical property that depends on the strength of the intermolecular forces between its molecules and the pressure exerted on the system. For oxygen, the boiling point is relatively low due to the weak London dispersion forces between its nonpolar molecules.
The relationship between the boiling point and the intermolecular forces can be described by the following equation:
T_b = (ΔH_vap) / (R * ln(P_vap / P_atm))
Where:
– T_b is the boiling point (in Kelvin)
– ΔH_vap is the enthalpy of vaporization (in J/mol)
– R is the universal gas constant (8.314 J/mol·K)
– P_vap is the vapor pressure of the substance (in Pa)
– P_atm is the atmospheric pressure (101,325 Pa)
For oxygen, the enthalpy of vaporization (ΔH_vap) is 6.82 kJ/mol, which is relatively low compared to other substances. This, combined with the low intermolecular forces, results in the low boiling point of oxygen.
Factors Affecting the Boiling Point of Oxygen
The boiling point of oxygen can be affected by several factors, including:
- Pressure: The boiling point of a substance is inversely proportional to the pressure exerted on the system. As the pressure increases, the boiling point increases, and vice versa. This relationship is described by the Clausius-Clapeyron equation:
ln(P_2 / P_1) = (ΔH_vap / R) * (1/T_1 - 1/T_2)
Where:
– P_1 and P_2 are the vapor pressures at temperatures T_1 and T_2, respectively.
– ΔH_vap is the enthalpy of vaporization.
– R is the universal gas constant.
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Impurities and Other Gases: The presence of impurities or other gases in the system can affect the boiling point of oxygen. Impurities can interact with the oxygen molecules, altering the intermolecular forces and, consequently, the boiling point.
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Molecular Structure: The molecular structure of a substance can also influence its boiling point. Substances with stronger intermolecular forces, such as hydrogen bonding, generally have higher boiling points compared to substances with weaker intermolecular forces, such as London dispersion forces.
Measuring the Boiling Point of Oxygen
The boiling point of a liquid, including oxygen, can be measured with a high degree of accuracy using various techniques, such as:
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Thermometer: A thermometer can be used to measure the temperature at which the liquid begins to boil. The boiling point is the temperature at which the vapor pressure of the liquid equals the surrounding atmospheric pressure.
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Distillation Apparatus: A distillation apparatus can be used to measure the boiling point of a liquid. The liquid is heated, and the temperature at which the vapor condenses is recorded as the boiling point.
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Phase Diagram: A phase diagram can be used to determine the boiling point of a substance. The phase diagram shows the relationship between the pressure, temperature, and phase of a substance.
When measuring the boiling point of a liquid in the lab, the results may look like this:
| Trial | Boiling Point |
|---|---|
| 1 | 122.0°C ± 0.1 |
| 2 | 222.1°C ± 0.1 |
| 3 | 321.9°C ± 0.1 |
These values represent the mean boiling point of the liquid, along with the uncertainty or error associated with the measurement.
Predicting the Boiling Point of Oxygen-Containing Compounds
In addition to experimental measurements, the boiling point of a substance can also be predicted using theoretical models or empirical correlations. One such approach is the use of a quantitative structure-property relationship (QSPR) strategy to predict the normal boiling point of oxygen-containing organic compounds.
The QSPR approach involves the use of mathematical equations or machine learning algorithms to correlate the boiling point with other molecular descriptors, such as the molecular weight, the polarizability, or the dipole moment. By using a large dataset of known compounds, the QSPR model can then be used to predict the boiling point of new or unknown compounds with a reasonable degree of accuracy.
For example, the following QSPR model can be used to predict the normal boiling point of oxygen-containing organic compounds:
T_b = 198.2 + 0.0146 * MW - 0.00113 * MW^2 + 0.000000345 * MW^3
Where:
– T_b is the normal boiling point (in Kelvin)
– MW is the molecular weight of the compound (in g/mol)
This model was developed by Katritzky et al. and has been shown to provide accurate predictions for a wide range of oxygen-containing organic compounds.
Conclusion
The boiling point of oxygen (O₂) under standard atmospheric conditions is a well-defined physical property that can be measured or predicted with a high degree of accuracy. The boiling point is affected by the strength of the intermolecular forces and the pressure exerted on the system, and can be influenced by the presence of impurities or other gases.
By using experimental measurements, theoretical models, or empirical correlations, the boiling point of a substance can be determined with a high degree of confidence, which is essential for various applications in chemistry, physics, engineering, and other fields.
References
- Boiling point of oxygen. In Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Boiling_point_of_oxygen
- Normal Boiling Points for Organic Compounds: Correlation and Prediction. In ACS Publications. Retrieved from https://pubs.acs.org/doi/abs/10.1021/ci970029v
- Revision chapter 1 1 .docx. In Course Hero. Retrieved from https://www.coursehero.com/file/42797298/Revision-chapter-1-1docx/
- Real Gases – Deviations from Ideal Behavior. In Chemistry LibreTexts. Retrieved from https://chem.libretexts.org/Bookshelves/General_Chemistry/Map:_Chemistry_-_The_Central_Science_%28Brown_et_al.%29/10:_Gases/10.09:_Real_Gases_-_Deviations_from_Ideal_Behavior
- Normal Boiling Points for Organic Compounds: Prediction and Correlation. In Semantic Scholar. Retrieved from https://www.semanticscholar.org/paper/Normal-Boiling-Points-for-Organic-Compounds%3A-and-by-Katritzky-Lobanov/0be288371e1f6c6d23d780899ea69d4bef3f302b/figure/2
- What is the boiling point of O2 under standard atmospheric conditions? In ProPrep. Retrieved from https://www.proprep.com/questions/what-is-the-boiling-point-of-o2-under-standard-atmospheric-conditions
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