Which of the following relationships is valid only for reversible process undergone by a closed system of simple compressible substance (neglect changes in kinetic and potential energy?

For an ideal gas the expression $$\left[ {T{{\left( {{{\delta s} \over {\delta T}}} \right)}_p} - T{{\left( {{{\delta s} \over {\delta T}}} \right)}_v}} \right]$$ is always equal to :

A system undergoes a state change from $$1$$ to $$2.$$ According to the second law of thermodynamics, for the process to be feasible, the entropy changes, $${S_2} - {S_1}$$ of the system

The slopes of constant volume and constant pressure lines in the $$T$$-$$s$$ diagram are ___________ and ___________respectively.