Question

For which of the following processes is $\Delta S$ negative?
a. $H_2\left(g\right)⟶2H\left(g\right)$
b. $N_2(g,1atm)⟶N_2(g,5atm)$
c. $2S{O}_3\left(g\right)⟶2S{O}_2\left(g\right)+O_2\left(g\right)$
d. $C\left(diamond\right)⟶C\left(graphite\right)$

• A. a
• B. b
• C. c
• D. None of these

Answer 1

The correct option is B b

Entropy is a state function that is often erroneously referred to as the 'state of disorder' of a system. Qualitatively, entropy is simply a measure how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probablities of a system or in terms of the other thermodynamic quantities.
$H_2\left(g\right)⟶2H\left(g\right)$ entropy increases because no of atoms increases.
$N_2(g,1atm)⟶N_2(g,5atm)$ entropy decreases as pressure increased and randomness decreases.
$2S{O}_3\left(g\right)⟶2S{O}_2\left(g\right)+O_2\left(g\right)$ entropy increases because no of atoms increases.
$C\left(diamond\right)⟶C\left(graphite\right)$ entropy increases as compactness of system decreases and randomness increases.