Question

Which of the following reactions results in a decrease in entropy? 2SO2 (g) + O2 (g) yields 2SO3 (g) 2NH3 (g) yields N2 (g) + 3H2 (g) 2H2O2 (aq) yields 2H2O (l) + O2 (g) NaHCO3 (aq) + HCl (aq) yields NaCl (aq) + H2O (l) + CO2 (g)

Answer 1

2SO2 (g) + O2 (g) yields 2SO3 (g)

Answer 2

Answer: Option (a) is the correct answer.

Explanation:

Entropy is defined as the degree of randomness of a substance.

For example, gases have more entropy as compared to liquids because molecules a gas have more kinetic energy due to which they move rapidly.

Also, when more number of moles are formed a chemical reaction then it means entropy has increased. But when there are less number of moles formed then it means there is a decrease in entropy.

Thus, we can conclude that the reaction $2SO_{2}(g) + O_{2}(g) \rightarrow 2SO_{3}(g)$ results in a decrease in entropy as 3 moles is giving 2 moles.