Question

For which of the following processes, $\Delta S$ is negative ?

• A. $H _{2}( g ) \rightarrow 2 H ( g )$
• B. $N _{2}( g , 1 atm ) \rightarrow N _{2}( g , 5 atm )$
• C. $C ($ diamond $) \rightarrow C ($ graphite $)$
• D. $N _{2}( g , 273 K ) \rightarrow N _{2}( g , 300 K )$

Answer 1

Answer: (B)

$N _{2}( g , 1 atm ) \rightarrow N _{2}( g , 5 atm )$

Answer 2

The higher the pressure, the lower is the entropy. When pressure increase on the gases, the kinetic energy of the particles decrease along with the pressure. This causes the particles to come closer and intermolecular distance decreases thus the entropy decreases.