Question

Which of the following processes are spontaneous? a. Salt dissolves in \(\mathrm{H}_{2} \mathrm{O}\). b. A clear solution becomes a uniform color after a few drops of dye are added. c. Iron rusts. d. You clean your bedroom.

Short answer

Processes a, b, and c (salt dissolves in \(\mathrm{H}_2 \mathrm{O}\), a clear solution becomes a uniform color after adding dye, and iron rusts) are spontaneous as they occur naturally without external intervention and increase the entropy of the system. Process d (cleaning your bedroom) is non-spontaneous, as it requires external intervention and decreases entropy.

Step-by-step solution

Process a: Salt dissolves in \(\mathrm{H}_2 \mathrm{O}\)

Salt dissolving in water is a spontaneous process because it occurs naturally without any external intervention. In this process, the salt ions interact with water molecules, and the dissolution takes place based on the electrostatic attraction between them. This process increases the entropy (disorder) of the system, making it spontaneous.

Process b: A clear solution becomes a uniform color after a few drops of dye are added

When a few drops of dye are added to a clear solution, the dye molecules spread throughout the solution to give a uniform color. This process is also a spontaneous process, as it occurs naturally without external intervention. The molecules of dye are distributed evenly in the solution by diffusion, and this process increases the overall entropy of the system, contributing to its spontaneity.

Process c: Iron rusts

Iron rusting is a spontaneous process because it occurs naturally in the presence of air and moisture. When iron comes in contact with air and water, it forms iron oxide or rust. This process is a slow chemical reaction, known as oxidation, and it leads to an increase in entropy. This increase in entropy makes the process of iron rusting spontaneous.

Process d: You clean your bedroom

Cleaning your bedroom is a non-spontaneous process because it requires external intervention (in this case, your effort) to organize and decrease the overall entropy of the system (your bedroom). The natural tendency of things is towards an increase in entropy, which is opposite to the result of cleaning your bedroom. As the process relies on external intervention and decreases entropy, it is considered non-spontaneous.