Estimate whether the entropy of the system increas...

Question

Estimate whether the entropy of the system increases or decreases during each process.
(a) photodissociation of O₂ (g),
(b) formation of ozone from oxygen molecules and oxygen atoms,
(c) diffusion of CFCs into the stratosphere,
(d) desalination of water by reverse osmosis.

Jules Bruno · Accepted Answer

In this problem, we are asked whether the entropy of the system increases or decreases during each of the given processes. Recall that entropy is the degree of chaos or disorder of a system. For a given process, entropy (ΔS) will either increase or decrease.We are given the following processes: (a) photodissociation of O2 (g),(b) formation of ozone from oxygen molecules and oxygen atoms,(c) diffusion of CFCs into the stratosphere,(d) desalination of water by reverse osmosis.[readmore]To solve this problem, remember that generally, the entropy of the system would increase for the following processes:Gases form from either solid to liquidLiquid or solutions form from solid.The number of molecules increases during the chemical reaction.(a) The photodissociation of O2(g) has a chemical reaction of:        O2(g) → 2 O(g)We can see that there is an increase in the number of moles in the product of the chemical reaction, the reaction produces 2 moles of O gas from one mole of oxygen molecule gas, thus, the entropy of the system increases.(b) The formation of ozone from oxygen molecules and oxygen atoms have the following chemical reaction:       O + O2 → O3In the reaction, we can see that there is a decrease in the number of molecules from 2 in the reactant to only 1 in the product, therefore, in this process, the entropy of the system decreases.(c) The chemical reaction for the diffusion of CFCs into the stratosphere is:   CF2Cl2(g) →  CF2Cl(g) + Cl(g)In the reaction above, we can see that there is an increase in the number of molecules in the product from the reactant, thus the entropy of the system increases.(d) In the desalination of water by reverse osmosis means that the solution moves from the area of lower concentration to the area of higher concentration.Recall that in osmosis the solvent moves from higher concentration to lower concentration. In this process, the entropy of the system would increase because of the distribution of the particles from the larger concentration to the smaller one.For the desalination of water, since it undergoes reverse osmosis, the opposite of the entropy of osmosis would be in effect, thus the entropy of this process decreases.Therefore, in the photodissociation of O2(g) and the diffusion of CFC the entropy of the system increases, while in the formation of ozone (O3) and the desalination process the entropy of the system decreases.

Problem: Estimate whether the entropy of the system increases or decreases during each process.(a) photodissociation of O2 (g),(b) formation of ozone from oxygen molecules and oxygen atoms,(c) diffusion of CFCs into the stratosphere,(d) desalination of water by reverse osmosis.

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Problem: Estimate whether the entropy of the system increases or decreases during each process.(a) photodissociation of O2 (g),(b) formation of ozone from oxygen molecules and oxygen atoms,(c) diffusion of CFCs into the stratosphere,(d) desalination of water by reverse osmosis.

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