The question asks for the modern, electron-transfer-based definition of reduction. This concept is fundamental in chemistry, particularly in redox reactions. We need to recall the definitions of oxidation and reduction in terms of electron transfer.
A) Gains one or more electrons — This is the correct modern definition of reduction based on electron transfer. When a substance gains electrons, its oxidation state decreases, which is characteristic of reduction.
The question asks for the best definition of a redox reaction. To answer this, we need to recall the fundamental principles of oxidation and reduction and how they relate to each other in a chemical reaction.
A) Oxidation and reduction occur simultaneously, with one substance being oxidised while another substance is correspondingly reduced. This statement perfectly encapsulates the definition of a redox reaction. The transfer of electrons from one species to another means that oxidation (loss of electrons) and reduction (gain of electrons) must happen concurrently.
The question asks to classify the process of rust formation. Rusting is a common chemical process involving iron, oxygen, and moisture. We need to identify the type of chemical change that occurs based on the definitions of physical change, reduction, neutralisation, and oxidation.
Correct Option: D) A type of oxidation (and corrosion), since the iron metal is losing electrons and combining with oxygen. This accurately describes the chemical process of rusting, where iron undergoes oxidation (loses electrons) and combines with oxygen to form iron oxide, which is a form of corrosion.
The question asks about the fundamental process driving corrosion. Corrosion is defined as the degradation of metals due to reaction with substances like oxygen, moisture, and acids. We need to identify the core chemical reaction type responsible for this degradation.
B) Oxidation reactions — Corrosion is fundamentally an electrochemical process where the metal loses electrons (gets oxidized) and reacts with environmental elements like oxygen and water to form more stable compounds (e.g., oxides, hydroxides). Therefore, oxidation is the primary driving force.
Rancidity is a common phenomenon observed in food items rich in fats and oils. Understanding the chemical processes involved is crucial for food preservation. The question asks for the primary chemical process responsible for rancidity when food is exposed to air.
C) Aerial oxidation of the fats and oils present in the food — This option accurately describes the chemical process. "Aerial oxidation" specifically refers to oxidation by oxygen from the air. This process leads to the formation of short-chain volatile compounds that impart off-flavors and odors.
The question asks why aluminium, despite being reactive, resists corrosion. This involves understanding the chemical properties of aluminium, particularly its interaction with oxygen.
D) It rapidly forms a thin, protective layer of aluminium oxide (Al₂O₃) on its surface, which effectively prevents further oxidation of the underlying metal. This option accurately describes the passivation process that makes aluminium resistant to corrosion.