The correct answer to the question is option 2: Exfoliation.

Chemical weathering is a process where chemical reactions break down rocks and minerals, leading to their decomposition and alteration. It is important to note that in chemical weathering, the rock`s composition changes due to chemical reactions.

Option 1: Hydration is a process of chemical weathering. It involves the absorption of water molecules into the mineral structure of rocks, causing them to expand and contract, leading to their disintegration.

Option 3: Oxidation is also part of chemical weathering. It refers to the reaction of rocks and minerals with oxygen in the presence of water, resulting in the formation of new compounds. This process contributes to the breakdown of rocks, such as the rusting of iron minerals.

Option 4: Solution is a process where minerals dissolve in water, altering the composition of rocks. It is another example of chemical weathering.

Option 2: Exfoliation, however, is not part of chemical weathering. Exfoliation is a physical weathering process that occurs when layers of rocks peel or flake off due to changes in temperature or pressure. It does not involve any chemical reactions.