What is the unit of entropy?

In which state does matter have the highest entropy?

For the reaction $A + B \rightarrow C + D + q$,which has a positive entropy change,the reaction:

When the same quantity of heat is absorbed by a system at two different temperatures $T_{1}$ and $T_{2}$,such that $T_{1} > T_{2}$,the changes in entropy are $\Delta S_{1}$ and $\Delta S_{2}$ respectively. Then:

One mole of an ideal diatomic gas $(C_V = 5 \ cal)$ was transformed from initial $25 \ ^{\circ}C$ and $1 \ L$ to the state when temperature is $100 \ ^{\circ}C$ and volume $10 \ L$. The entropy change of the process can be expressed as $(R = 2 \ cal / mol \cdot K)$ :-

Provide the mathematical equation for entropy change.