Question

In which of the following processes does the entropy increase? In each case, explain why it does or does not increase. (a) A bottle of ammonia is opened. The odor of ammonia is soon apparent throughout the room. (b) Sodium chloride dissolves in water. (c) A protein is completely hydrolyzed to the component amino acids.

Short answer

Entropy increases in all processes (a), (b), and (c) because they all result in greater disorder.

Step-by-step solution

- Understanding Entropy

Entropy is a measure of the disorder or randomness of a system. An increase in entropy means the system becomes more disordered. Whenever particles spread out or separate, entropy typically increases.

- Evaluating Process (a)

(a) When a bottle of ammonia is opened, the ammonia molecules spread out from a high concentration inside the bottle to a lower concentration throughout the room. This increase in the distribution of molecules signifies an increase in entropy due to the greater randomness and disorder in the system.

- Evaluating Process (b)

(b) When sodium chloride dissolves in water, the orderly crystal lattice of the solid salt breaks down into individual ions, which then disperse through the solvent. This process increases the disorder of the system, and therefore, the entropy of the system increases.

- Evaluating Process (c)

(c) When a protein is completely hydrolyzed to its component amino acids, the long and ordered polypeptide chain is broken down into individual amino acids. The breakdown of a structured molecule into its more disordered components increases the entropy of the system.

Key concepts

entropy increase

Entropy is a measure of disorder or randomness in a system. The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. In simpler terms, nature tends to progress towards a state of higher disorder. When processes occur where particles spread out or systems become more random, entropy increases. Let's explore specific examples to understand this better.

ammonia diffusion

Imagine you open a bottle of ammonia in a room. Initially, the ammonia molecules are concentrated in the bottle. The moment you open it, these molecules start spreading out across the room. This process is known as diffusion. The ammonia molecules move from an area of high concentration inside the bottle to areas of lower concentration throughout the room.

As the ammonia molecules disperse, they increase in randomness. Consequently, the entropy, or disorder, of the system increases. This happens because there are now more ways to arrange the ammonia molecules in the space compared to when they were all confined in the bottle.

sodium chloride dissolution

When sodium chloride (table salt) dissolves in water, an interesting process occurs. Solid sodium chloride has a well-ordered crystal lattice structure. When placed in water, this structure breaks down, and the individual sodium (Na⁺) and chloride (Cl^-) ions disperse throughout the liquid.

The dissolving process disrupts the orderly arrangement of the salt crystal, increasing randomness and thus the entropy of the system. The ions spread out and interact with the water molecules more freely, representing a state of higher disorder compared to the solid form of sodium chloride.

protein hydrolysis

Proteins are large, complex molecules made up of long chains of amino acids. These chains fold into specific shapes to perform various functions in biological systems. When a protein undergoes hydrolysis, it is broken down into its component amino acids.

During this process, the structured and orderly arrangement of the protein molecule is dismantled into many smaller, more randomly arranged amino acid molecules. This breakdown leads to an increase in entropy because the system has transitioned from a state of lower disorder (the folded protein) to a state of higher disorder (the dispersed amino acids).