What is at 298 K at standard entropy?

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298K refers to the temperature of the substance and its surroundings. 298K is about 25 degrees Celsius. In other words, the statement can be simplified as:

The standard entropy of a substance is the entropy of 1 mol at room temperature and pressure.

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inspd
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Updated on August 15, 2022

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  • inspd
    inspd about 1 year

    The standard entropy of a substance is the entropy of $1$ mol at $298$K and $1$ bar pressure.

    What exactly is at $298$K? The system or the surrounding?

    Let's take vapour as an example where $ \ \ce{H2O(g)} \ \ \ \ S^{\Phi}_{298}\approx188.8 \ JK^{-1}mol^{-1}$. Is the $298$K referring to the temperature of the gaseous $\ce{H2O}$? I'm confused.

  • inspd
    inspd over 7 years
    the part that's confusing me is if the substance $H_{2}O$ is also at $25ºC$ then how can we say it is a gas and find its entropy?
  • IT Tsoi
    IT Tsoi over 7 years
    As you mention, vapor, is water in the gas phase at temperatures lower than 100 oC. That's like humidity.