Question

Are enthalpy and entropy affected by temperature?

Answer 1

Yes, they are. Here is how:

`DeltabarS = int_(T_1)^(T_2) (barC_P)/T dT`

`DeltabarH = int_(T_1)^(T_2) barC_P dT`

where `barC_P` is the molar heat capacity in a constant pressure system, and `DeltaS` and `DeltaH` are the change in entropy and enthalpy, respectively.

So, let's say you had water, whose chemistry molar heat capacity is defined as `"75.375 J/mol"*"K"`. Then, we have, from `273` to `"298 K"`:

`DeltabarS = int_("273 K")^("298 K") (barC_P)/T dT`

`= barC_P|[ln|T_2| - ln|T_1|]|_("273 K")^("298 K")`

`= 75.375*(ln(298) - ln(273))`

`color(blue)("= 6.604 J/mol"*"K")`

`DeltabarH = int_("273 K")^("298 K") barC_P dT`

`= barC_P(T_2 - T_1)`

`= 75.375(298 - 273)`

`color(blue)("= 1884.38 J/mol")`