Carbon monoxide (CO) is a neutral oxide, meaning it does not react with acids or bases to form salts. In contrast, SO2, SO3, and NO2 are acidic oxides because they react with water to form acidic solutions (sulfurous, sulfuric, and nitric/nitrous acids, respectively).

CO2 is not considered poisonous in low concentrations, though it can cause asphyxiation. It is an acidic oxide because it forms carbonic acid in water. It reacts with calcium hydroxide (lime water) to form calcium carbonate, which turns the solution milky.

Aqua regia is a highly corrosive, fuming liquid mixture of concentrated nitric acid and concentrated hydrochloric acid, typically in a 1:3 volume ratio. It is one of the few reagents capable of dissolving noble metals like gold and platinum.

Mercury is used in thermometers primarily due to its high coefficient of thermal expansion and its ability to remain liquid over a wide temperature range. The term 'circulation power' in this context refers to its uniform and rapid expansion/contraction properties, allowing for accurate and consistent temperature readings across the scale.

Soft drinks are carbonated by dissolving carbon dioxide gas in water under pressure. This process produces carbonic acid (H2CO3), which gives the beverage its characteristic tangy taste and effervescence. While other acids like citric acid may be added for flavoring, carbonic acid is the primary agent responsible for the carbonation process.

The bleaching action of moist sulphur dioxide is primarily due to its ability to act as a reducing agent. In the presence of moisture, sulphur dioxide reacts to form nascent hydrogen, which reduces colored organic matter to a colorless state. This process is temporary, as the bleached material can often regain its color upon exposure to atmospheric oxygen, which re-oxidizes the reduced product.

Silver reacts with atmospheric sulphur compounds, such as hydrogen sulphide, to form a layer of silver sulphide (Ag2S). This compound is black in color, which is why silver jewelry or utensils tarnish when exposed to air containing sulphur impurities over time.

Chloropicrin (trichloronitromethane) is a chemical compound historically used as a lachrymatory agent, commonly known as tear gas. It acts as an irritant to the eyes, respiratory tract, and skin. While other substances like CS gas (2-chlorobenzalmalononitrile) are more commonly used in modern riot control, chloropicrin remains a classic example of a lachrymator in chemical literature and historical contexts.

White phosphorus is highly reactive and has a low ignition temperature. When exposed to oxygen in the air, it undergoes rapid oxidation, which generates enough heat to cause it to ignite spontaneously, producing a characteristic white smoke of phosphorus pentoxide. Due to this property, it is typically stored under water to prevent contact with air.

Sulphur commonly exists as an S8 molecule, which is a puckered ring structure. Phosphorus also exists as P4, but sulphur is a classic example of a polyatomic element. Argon is mono-atomic, and chlorine is diatomic (Cl2).