The properties of a substance change with temperature and pressure
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This post was last edited by “19th Floor Inspector” on July 4, 2011, at 08:08. I have a question: there’s a substance that is in a gaseous state at room temperature; when pressure is applied, it becomes liquid. In subsequent processes, the pressure decreases, resulting in a mixture of liquid and gas. I’d like to know the ratio between them. The example above is just one instance; what I want to ask is: generally, as pressure increases, the boiling point of a substance rises as well ； As pressure decreases, the boiling point also decreases, right? ? Who can tell me how to calculate this ratio? At what state does the phase change occur? (For example, HF has a boiling point of 20 degrees.) At room temperature in summer, it is in the gas phase; so what pressure needs to be applied to make it react in a liquid state?
1. Generally, the boiling point of a substance increases as pressure rises； As pressure decreases, the boiling point also decreases. For mixtures, at different pressures the partial pressure of the vapor phase components remains constant; the gas-liquid ratio can be determined using the gas-liquid equilibrium conditions. 2. Critical pressure is mentioned among the general properties of substances; above this pressure, the substance cannot vaporize no matter what the temperature is, while below this pressure, temperature can cause liquefaction
Thank you, I want to figure out the variation curve of a single substance. It’s not about purifying the mixture; now we need to change the gas-liquid state in order to proceed.