[Foobarz]

So, if entropy changes with temperature, then why is it in units of J/K*mol?
Do I have to multiply the temperature by the difference in entropy values to obtain J/mol?

[UG]

Not sure what you are asking, the enthalpy also changes with temperature...

[Sophia7X]

I'm not sure what you exactly mean. Entropy's unit is in J/K, standard molar entropy is in J/K*mol (the entropy for one mole of a substance).

"To obtain J/mol" units... well entropy isn't in j/mol. But you can plug delta S into the Gibbs free energy equation to get kJ/mol. Gibbs free energy is not the same as entropy.

ΔG = ΔH - TΔS

Units: ΔG and ΔH are in kJ/mol
T in Kelvin, and ΔS is usually in J/K*mol so you can convert it to kJ/K*mol to match the units.
So you do multiply T and ΔS (that's only part of it). It cancels out the K.

Hopefully this can be of some help.

[Foobarz]

Ok then if Gibbs free energy is G=H-TS

then  :delta:G= :delta:H- :delta:(TS) ?

But why is :delta:G= :delta:H-T :delta:S ? at constant temperature?

Cause if temperature is constant, then shouldn't  :delta:T be 0? and  :delta:G= :delta:H?

[Foobarz]

OK OK OK SCRATCH THAT its  :delta:(TS) not  :delta:T :delta:S

So of course yeah if T is constant, its just  T :delta:S

[Sophia7X]

You are not measuring a change in temperature.

T simply represents any temperature. For example, if you want a constant temperature, just plug that one temperature in.

Let's say temperature increases from 298 K to 320 K.
You need to have 2 Gibbs free energy equations. Plug in 298 K for T for one of them and 320 K for the other.
ΔG1 = ΔH - 298ΔS
ΔG2 = ΔH - 320ΔS

If you calculated the change in G, you can see that T does have an effect because G1 and G2 will have different values.

[juanrga]

So, if entropy changes with temperature, then why is it in units of J/K*mol?
Do I have to multiply the temperature by the difference in entropy values to obtain J/mol?

The units of entropy are J/K because entropy gives energy per temperature.

The entropy function for simple systems is S=S(U,V,N) where U is internal energy, V is volume, and N is amount of matter.

Moreover, U can be expressed as a function of temperature and substituting back you can find a function S=S(T,V,N)