Chemical Compounds and Reactions

Silver nitrate (AgNO3) is historically called Lunar Caustic because silver was associated with the moon (luna). It was used as a caustic agent for cautery. The other options are not recognized common names for silver nitrate.

Indian red is ferric oxide (Fe2O3), a naturally occurring red pigment used in paints and dyes. It's not zinc sulfate, ferrous oxide (FeO), or aluminum sulfate - those are completely different compounds. The red color comes from the iron in the +3 oxidation state.

Oxygen (O2) is essential for sustaining life on Earth as it is required for cellular respiration in most organisms. While water (H2O) is also vital, the question specifically asks for a nonmetal, and O2 is the elemental form of oxygen that supports aerobic life. K4H2O2 and P2O are not standard chemical formulas for life-sustaining substances.

Hygroscopic salts absorb moisture from the atmosphere without dissolving in it. Anhydrous salts are simply without water of crystallization, while hydrophilic refers to water-attracting substances more generally. Hydrophobic substances actually repel water.

Zinc oxide is the white cream (often called 'zinc' or 'white sunscreen') applied by cricketers on their faces, specifically under the eyes and on the nose. It provides sun protection by reflecting UV rays and also helps reduce glare from sunlight. Vaseline is a petroleum jelly used for moisturizing, while nitrous oxide is a gas used as anesthetic - not applied on skin.

Chromium(II) is Cr2+. Sulfate (SO4) has a -2 charge. They cancel in a 1:1 ratio, giving CrSO4. Cr2SO4 would be Cr4+, and Cr(SO4)2 would require Cr4+.

Saccharin (the correct spelling) was discovered in 1879 by researchers working with coal tar derivatives, making it historically a coal-derived product. The accidental discovery occurred during experiments on coal tar compounds at Johns Hopkins University.

Silver(I) chloride, also called argentous chloride, has the chemical formula AgCl - formed from silver (Ag) and chlorine (Cl). It's a white insoluble solid sensitive to light. NaOH is sodium hydroxide, HCl is hydrochloric acid, and KBr is potassium bromide.

Mercury is a liquid metal at room temperature that forms small, shiny droplets. These droplets can easily roll and scatter when disturbed, which is why it's historically called 'quicksilver.' The other options (paint, bleach, water) don't share this characteristic behavior.

Different metal salts produce characteristic flame colors in fireworks: barium compounds give green, strontium gives red, copper gives blue, and sodium gives intense yellow. This occurs because the metal atoms absorb energy and release it as specific wavelengths of visible light. Mercury and potassium don't produce green flames in this context.

The passage uses the word 'regretfully' to express disapproval of chemical agents in warfare. The author criticizes those who view chemical weapons as useful tools, making it clear that their use is undesirable. Option C correctly captures this critical stance toward chemical warfare.

Excess of nitrates in drinking water causes methaemoglobin formation which results in blue baby syndrome or  methemoglobinemia.

Ammonium dichromate is an inorganic compound with the formula (NH₄)2Cr₂O₇. It is a salt consisting of ammonium ions and dichromate ions. It has been used in pyrotechnics and in the early days of photography as well as in lithography, as a source of pure nitrogen in the laboratory, and as a catalyst.

It reduces acidified potassium dichromate solution to a green-coloured chromic salt.

It decolourises KMnO₄.