The variation of entropy with temperature

For a reversible change the entropy increment is dS1 = dq/T. The variation of the entropy from T to 73 is therefore given by 

For a process taking place at constant pressure and that does not involve any non-pV work 

The entropy of a particular compound at a specific temperature can be determined through measurements of the heat capacity as a function of temperature, adding entropy increments connected with first-order phase transitions of the compound  

Equation (1.53) applies to each substance in a reaction and a change in the standard entropy of a reaction (p is now p° = 1 bar) going from T to T2 is given by (neglecting for simplicity first-order phase transitions in reactants and products) 

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The variation of entropy with temperature can also be expressed using the specific heat capacity Cp. From classical thermodynamics... 

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