Air can oxidize sodium sulphate in aqueous solution but cannot do so in the case of sodium arsenite. If, however, air is passed through a solution containing both sodium sulphite and sodium arsenite then both are oxidized. This is an example of (a) Positive catalysis (b) Negative catalysis (c) Induced catalysis (d) Auto catalysis

Chemical oxidation is a fundamental process where a substance loses electrons, a scenario often seen in combination with the gain of oxygen or the loss of hydrogen. In an aqueous solution, the availability of oxygen from air can lead to the oxidation of certain compounds.

For example, in the exercise given, sodium sulfite can be oxidized by air. This is because it can readily lose electrons in the presence of oxygen. However, oxidation isn't always a straightforward process. Certain compounds like sodium arsenite may require specific conditions or a helping hand, such as the presence of another substance, to undergo oxidation.

Understanding these nuances is crucial, as oxidation reactions are pervasive in chemistry, with applications ranging from industrial processes to biological systems. By mastering the concept of chemical oxidation, students can better comprehend how substances interact with their environment and each other on an electron level.

Catalysis, the process of accelerating a chemical reaction by the addition of a substance called a catalyst, comes in various forms. Here are the major types briefly explained:

• Positive Catalysis: Increases the reaction rate. This type occurs when a catalyst provides an alternative pathway with a lower activation energy.
• Negative Catalysis: Decreases the reaction rate, which can happen when a substance interferes with the reactants or the catalyst, lowering the rate at which products form.
• Induced Catalysis: A process where one reaction influences another. The reaction of one substance is made possible or sped up by the reaction of another substance, even if the second substance doesn’t directly interact with the initial reactant.
• Auto Catalysis: When the product of the reaction itself acts as a catalyst, the reaction rate increases as the concentration of the product builds up.

The exercise provided is an excellent illustration of induced catalysis. When students encounter such examples and correctly identify the type of catalysis, they deepen their understanding of how substances can influence the reactivity of one another, which is a cornerstone in chemical kinetics.

Redox reactions, short for reduction-oxidation reactions, involve the transfer of electrons between substances. They are essentially a combination of two processes: oxidation, where a substance loses electrons, and reduction, where a substance gains electrons.

In the context of the exercise, when sodium sulfite and sodium arsenite are in a solution, they participate in a redox reaction with the oxygen from air. Sodium sulfite is oxidized more readily and in doing so, it influences the redox state of sodium arsenite, leading to its oxidation - this is the core of induced catalysis.

To comprehend redox reactions fully, students should visualize them as a dance of electrons from one substance to another. The partners in this dance (the substances) can change their roles (get oxidized or reduced) under different conditions. By appreciating the delicate balance of electron transfer, learners unlock a deeper understanding of many chemical processes, from energy production in batteries to the metabolic pathways in living cells.