Which one of the following is not an oxidation reaction?

Which one of the following is not an oxidation reaction?

Rusting of iron
Opening of soda bottle
Rancidity
Combustion
This question was previously asked in
UPSC CDS-1 – 2023
The correct answer is B) Opening of soda bottle. This is a physical process involving the release of dissolved carbon dioxide gas due to reduced pressure upon opening the bottle. It does not involve a chemical reaction where a substance loses electrons or gains oxygen (oxidation).
– Oxidation is a chemical process involving the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. It often involves reaction with oxygen.
– Rusting of iron is the oxidation of iron in the presence of oxygen and moisture to form iron oxides (rust).
– Rancidity is the oxidation or hydrolysis of fats and oils, leading to unpleasant smells and flavors.
– Combustion is a chemical process (often rapid) between a substance and an oxidant, usually oxygen, to produce heat and light. It is typically an oxidation-reduction (redox) reaction.
While opening a soda bottle involves a release of energy (due to decreasing potential energy of the compressed gas), the fundamental process is a physical change of state and solubility due to pressure change, not a chemical oxidation reaction like rusting, rancidity, or combustion.