[erma79]

The molar heat capacity is defined as the amount of heat required to raise the temperature of one mole of substance by one degree K.

The molar capacity of Liquid water at 25 C is 75,3 J/(mol K)

The standard entropy of a substance (at 25 C then) is measured by determining the amount of heat required to raise the temperature of one mole of substance by 1 degree K.

The standard entropy of Liquid water is 69,6 J/(mol K)

By these two definitions, it seems to me this should be the case:

molar heat capacity at 25 C = standard entropy at 25 C.

This is not the case so obviously I am missing something, but what

[mjc123]

The standard entropy of a substance (at 25 C then) is measured by determining the amount of heat required to raise the temperature of one mole of substance by 1 degree K.

Where did you get that from? Just because they both have units of J/(mol K) doesn't mean they are the same thing.
The relation between them is dS/dT = C_p/T
S increases with temperature. C_p, to a first approximation, is usually fairly constant over a limited temperature range. The fact that your values of 75.3 and 69.6 are quite close is coincidental; change the temperature significantly and the entropy value will be quite different.
Moreover, the value of standard entropy depends on the standard state it's relative to. For example, though this page https://en.wikipedia.org/wiki/Water_(data_page) says the standard molar entropy is 69.95 J/(mol K), the data table 2/3 way down the page gives S at 25°C = 0.367 kJ/(kg K) = 6.61 J/(mol K), relative to S_liq = 0 at 0.01°C (triple point temp). What is the reference state for the 69.95 value? S_ice = 0 at 0K? They don't say.

[erma79]

The relation between them is dS/dT = C_p/T

[erma79]

I see. As you probably understand, physical chemistry isn't what I'm best at. Math I can handle just fine. Thanks for the quick answer!

[erma79]

Moreover, the value of standard entropy depends on the standard state it's relative to.

I thought all standard entropies were relative to S_{solid state}=0 at 0 K.