For a pure substance, at a certain external atmospheric pressure, the boiling point should be a constant value, right?
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This post was last edited by 2005180005 on 2021-3-8 09:37. Generally speaking, the boiling point of a substance is not a single value, but rather a range of temperatures, known as the boiling range. The purer a substance is, the shorter its boiling range. Pure liquid compounds have a very narrow boiling range during distillation, ranging from about 0.5 to 1°C. “The “initial boiling point” can be considered as the temperature at which the liquid begins to distill. The boiling point, on the other hand, is the temperature at which the saturated vapor pressure of a liquid equals the external pressure; it is a theoretically defined value. The above statement is incorrect, right? For a pure substance, at a certain external atmospheric pressure, the boiling point should be a fixed value, not a range
Theoretically, it is a fixed value, but in practice there may be slight variations. I think the views expressed in that passage are quite rigorous
What was said upstairs is correct; this statement is quite precise. As long as it is a number, it is set by humans. For example, the boiling point of water is set at 100°C for ease of calculation and memorization; the actual measured value is 99.975. This value also represents a range, and when compared to 100, it shows a deviation of 0.025, which is practically negligible. Even this 99.975 is actually the result of making some trade-offs; it could be 99.9751 or it could be 99.9749. The opposite is a fixed value. Strictly speaking, both compounds and mixtures are range values.
For pure substances, the boiling point remains constant at constant pressure