Chemistry of Gases and Applications

National highway signboards in India are made of retro-reflective sheeting materials that reflect light back to its source, making them visible at night. They are not made of gases like neon, hydrogen, or freon, making 'none of these' the correct answer.

Mustard gas is a poisonous chemical warfare agent that causes severe burns and respiratory damage. Hydrogen and oxygen are essential elements for life, while carbon dioxide is a natural byproduct of respiration that is not poisonous at normal concentrations.

Helium is classified as an inert gas (also known as a noble gas). Noble gases are characterized by having complete valence electron shells, making them extremely stable and unreactive under normal conditions. Tear gas is used for riot control, laughing gas is nitrous oxide (N2O), so these are incorrect.

Helium's chemical symbol is He, not H2. H2 represents hydrogen gas (two hydrogen atoms bonded together). The question asks for the WRONG combination, and Helium-H2 is indeed incorrect because H2 belongs to hydrogen, not helium.

The question asks for INCREASING order (least to most). Argon (~0.93%) is least abundant, then oxygen (~21%), then nitrogen (~78%). So argon < oxygen < nitrogen is correct. Option B states 'argon, oxygen and nitrogen' which matches this increasing order.

Carbon monoxide is extremely toxic because it binds to hemoglobin 240 times more strongly than oxygen, preventing oxygen transport and causing asphyxiation. CO2 and N2 are asphyxiants at high concentrations but less immediately toxic, while hydrogen is flammable but not typically described as 'toxic' in the same way as CO.

Ammonia gas is used in cold storage plants for refrigeration.

Acetylene gas (produced when calcium carbide reacts with water) is commonly used for artificial fruit ripening in commercial settings. Ethylene is the natural ripening hormone, but acetylene mimics its effects.

India's SLV-3 (Satellite Launch Vehicle-3) and ASLV (Augmented Satellite Launch Vehicle) used composite solid propellants based on HTPB (hydroxyl-terminated polybutadiene) binder with ammonium perchlorate oxidizer and aluminum fuel.

The Space Shuttle Main Engines (SSMEs) used liquid hydrogen (LH2) as fuel and liquid oxygen (LOX) as oxidizer in a staged combustion cycle. This combination produces a very high specific impulse and was essential for achieving orbit. Liquid hydrogen and liquid oxygen are each components of the propellant system, but the complete answer is the mixture of both.

The Titan II ballistic missile used a hypergolic propellant combination: unsymmetrical dimethylhydrazine (UDMH, a hydrazine derivative) as fuel and nitrogen tetroxide (N2O4) as oxidizer. Hydrazine (NH2NH2) and N2O4 ignite spontaneously on contact, which is critical for reliable missile ignition. The question's wording 'mixture of NH2NH2 and N2O4' is close enough to the correct hypergolic concept to accept as the intended answer, though Titan specifically used UDMH rather than pure hydrazine.

Carbon mono oxide is not a permanent part of the earth’s atmosphere. It is a pollutant but not a permanent part of the atmosphere.

Air is a mixture of many gases, primarily nitrogen (78%), oxygen (21%), and small amounts of carbon dioxide, argon, water vapour, and trace gases. It is not composed of just one or two gases.

Air contains many gases including nitrogen, oxygen, argon, carbon dioxide, water vapour, neon, helium, and trace gases. While nitrogen and oxygen make up 99% of air, there are definitely more than just two, three, or four gases present.

Oxygen, nitrogen, and carbon dioxide are fixed, permanent constituents of air. Water vapour is the odd one out because its concentration varies with location, temperature, and weather conditions (0-4% typically, but can be higher). It's the only variable component listed.