The following changes are performed on 1 mol of `N_(2)` gas-
(i) Pressure is decreased at constant at constant temperature.
(ii) volume is decreased at constant temperature.
What will be the sign of `DeltaS_(sys)` in these changes?

Explanation

(i) If the pressure of a gas is decreased at constant temperature, the volume of the gas increases. At a larger volume of a gas, the gas molecules gets greater chance to move about. As a result, the randomness of the molecules increases, which results in an increase in entropy of the gas. hence, `DeltaS_("sys")=+ve`.
(ii) At constant temperature, the decrease in volume of a gas reduces the availability of space for the movement of gas molecules. this results in a decrease in of gas molecules. this results in a decrease in randomness of the molecules, consequently, the entropy of the gas decreases. hence, `DeltaS_("sys")=-ve`.