Question

The change in entropy, Δ S ∘ rxn , is related to the the change in the number of moles of gas molecules, Δ n gas . Determine the change in the moles of gas for each of the reactions and decide if the entropy increases, decreases, or has little or no change. A. 2 H 2 ( g ) + O 2 ( g ) ⟶ 2 H 2 O ( l )

Answer 1

Answer:

The entropy decreases.

Explanation:

The change in the standard entropy of a reaction (ΔS°rxn) is related to the change in the number of gaseous moles (Δngas), where

Δngas = n(gaseous products) - n(gaseous reactants)

• If Δngas > 0, the entropy increases
• If Δngas < 0, the entropy decreases.
• If Δngas = 0, there is little or no change in the entropy.

Let's consider the following reaction.

2 H₂(g) + O₂(g) ⟶ 2 H₂O(l)

Δngas = 0 - 3 = -3, so the entropy decreases.