Question 7.5: Entropy Change of Processes Does entropy increase or decreas......
Entropy Change of Processes
Does entropy increase or decrease in the following processes?
(a) Smoke from a cigarette disperses throughout a room rather than remaining in a cloud over the smoker’s head.
(b) Water boils, changing from liquid to vapor.
(c) A chemical reaction occurs: 3 H_{2}(g) + N_{2}(g) → 2 NH_{3}(g)
ANALYSIS Entropy is a measure of molecular disorder. Entropy increases when the products are more disordered than the reactants; entropy decreases when the products are less disordered than the reactants.
(a) Entropy increases because smoke particles are more disordered when they are randomly distributed in the larger volume.
(b) Entropy increases because H_{2}O molecules have more freedom and disorder in the gas phase than in the liquid phase.
(c) Entropy decreases because 4 mol of reactant gas particles become 2 mol of product gas particles, with a consequent decrease in freedom and disorder.