Deriving Standard Molar Entropy of Water

[dbrittain]

Hello everyone, I am a second year physics student attending university, and I have a question about how the actual Standard Molar Entropy of various molecules are found and derived. I have been looking through various Thermodynamics and Chemistry books as well journals online and have all referenced water, for example, to have a standard entropy of around 70 (some are more specific, stating 63.45 J/mol-K etc, but others including some chemistry books state the standard molar entropy to be 69.9 J/mol-K.).

I am specifically interested in how the standard molar entropy of water in liquid form was found.

Thanks in advanced,

 

[Chestermiller]

If you know the standard molar entropy of gaseous water (a hypothetical state), the standard molar entropy of liquid water is that value minus the heat of vaporization divided by the standard absolute temperature. To get the standard molar entropy of liquid water, you need to measure (or otherwise know) the equilibrium constant for formation reaction.