Why are the published values of the boiling points of substances always taken at 1 atm?
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The published values of boiling points of substances are typically measured and reported at 1 atm (atmosphere) for standardization and ease of comparison. Here's why:
1. Standardization: Using a common pressure level, in this case, 1 atm, allows scientists and researchers to compare boiling points under similar conditions. It provides a reference point and enables meaningful comparisons across different substances.
2. Practicality: 1 atm is the atmospheric pressure at sea level, which is the most common and easily accessible pressure for most laboratory experiments. Since atmospheric pressure can vary with altitude and weather conditions, using a standard pressure eliminates variables and ensures consistent results for boiling point measurements.
3. Compatibility: Many laboratory techniques and instruments are calibrated and designed to function at or near atmospheric pressure. By using 1 atm, it aligns with the capabilities and parameters of common laboratory equipment used for measuring boiling points, such as boiling point apparatus or thermometers.
It's worth noting that when researchers need boiling point values under different pressure conditions, they can use thermodynamic relationships, such as the Clausius-Clapeyron equation, to calculate and account for the pressure variation. However, for simplicity and consistency, the standard practice is to report boiling point values at 1 atm.