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Tala97

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My chemistry final is approaching and I have a few difficulties in the thermodynamics chapter.

One of the things that are bothering me is the calculation of the temperature of phase change.

We know that if a mole of ice at 273K melts, the entropy change would be ΔS=ΔHf/T=6030/273=22.1J/K, we compare this to ΔSsurr and we find that their sum (ΔSuni) is 0.

But when we want to calculate ΔS at other temperatures to compare them with ΔSsurr, and see if the process is spontaneous, we always assume that ΔS is equal to 22.1J/K and that the heat needed to melt 1 mole is 6030J; as if when 1 mole of ice at 263K (-10 degrees Celsius) hypothetically melts its change of entropy would be the same as if it melted at 273K, and the heat it would need to change phases is not temperature dependent.

To quote the book : "In these calculations we are assuming ΔS and ΔH to be temperature independent".

To what extent is this true? Why would melting of ice at whatever temperature always cause an entropy change of the system by 22.1J/K, the same goes for ΔH.

Is there a formula that would give the hypothetical change in entropy of ice when it melts at diffrent temperatures so that I could see that temperature dependence is low?

And THANK YOU