Chemistry

Argon is known as the 'Stranger Gas' because it is chemically inert and was discovered as a new, 'strange' gas in the atmosphere that did not react with other elements. The other gases listed do not have this nickname.

The chemical symbol for Gold is 'Au', derived from its Latin name 'Aurum'. This is the standard symbol used in the periodic table.

Glycerol (also known as glycerin) is the alcohol used in the preparation of dynamite. It is nitrated to form nitroglycerin, the explosive compound in dynamite. The other alcohols listed are not used in this process.

The reaction between methane and chlorine in diffused sunlight proceeds via a radical substitution mechanism, where chlorine radicals replace hydrogen atoms in methane.

Natural gas, petroleum, and coal primarily consist of hydrocarbons, which are compounds made mostly of carbon atoms. Carbon forms the major part of these fossil fuels, making option A correct. Methane is a component of natural gas but not the major part of all three substances.

Dmitri Mendeleev is credited with creating the periodic table by arranging elements according to their atomic masses and properties, which allowed him to predict undiscovered elements.

Ruby is a red gemstone that is primarily composed of aluminum oxide (Al2O3), which is the mineral corundum. The red color of ruby is due to trace amounts of chromium replacing some aluminum atoms in the crystal structure. It is not an oxide of gold, silver, or platinum. Therefore, the correct answer is D, aluminium oxide.

Tungsten has the highest melting point among natural elements, at about 3422°C, which is significantly higher than iron, copper, or silver. This makes it the correct answer.

Sodium thiosulphate is commonly used as a fixer in photography to dissolve unexposed silver halide crystals from the photographic film or paper, making the image permanent and light-resistant.

Oil of vitriol is the historical name for sulfuric acid, a dense, oily liquid widely used in industry and laboratories.

Bleaching powder primarily contains chlorine, which is responsible for its bleaching and disinfecting properties. The other elements listed are not components of bleaching powder.

Ozone is a molecule composed of three oxygen atoms, so its chemical formula is O3. This distinguishes it from diatomic oxygen (O2) and other compounds listed in the options.

Copper toxicity, as seen in Wilson's disease, leads to copper accumulation in the liver causing liver damage and cirrhosis. Lead, mercury, and zinc do not typically cause liver cirrhosis through toxicity.

Hydrogen is the first element in the periodic table with atomic number 1, making it the lightest and simplest element.

Christian Friedrich Schönbein is credited with the discovery of ozone in the early 19th century. Ozone is a triatomic form of oxygen, distinct from the oxygen we breathe, and Schönbein identified it through his experiments.

Hydrofluoric acid (HF) cannot be stored in glass bottles because it reacts with silicon dioxide in glass, causing the glass to corrode and break down. Aqua regia, HCl, and HBr do not react with glass in the same way and can be stored safely in glass containers.

The term "Tezaab" commonly refers to sulfuric acid in everyday language, especially in South Asia. Among the options, sulfuric acid is the correct chemical name corresponding to "Acid" (Tezaab).

Mercury and bromine are the only two elements that are liquid at room temperature (around 20-25°C). Mercury is a metal and bromine is a halogen, both existing as liquids under standard conditions, unlike the other elements listed which are gases or solids at room temperature.

Radon is a noble gas but is not commonly present in the atmosphere in significant amounts because it is radioactive and has a short half-life, causing it to decay quickly. Argon, Helium, and Xenon are all present in the atmosphere in trace amounts.

Rainwater is considered the purest form of natural water because it is produced by evaporation, which leaves behind most dissolved solids and contaminants, making the initial condensed droplets essentially distilled water. However, as rain falls, it can pick up small amounts of dust, soot, and atmospheric gases such as carbon dioxide and sulfur dioxide, but these impurities are minimal (about 1/100,000th of its weight). Tap water is treated municipal water that contains residual disinfectants and minerals, making it less chemically pure than rainwater but safe for consumption. Heavy water (D2O) contains deuterium instead of hydrogen and is not a natural drinking water source; it is chemically pure in terms of lacking contaminants but isotopically different and used mainly for scientific purposes. Therefore, among the given options, rainwater is the purest form of water in terms of natural purity.

Graham's Law states that the rate of effusion of a gas is inversely proportional to the square root of its density (or molar mass). This means lighter gases effuse faster than heavier gases.

Hydrogen bonds are weaker than covalent bonds such as single, double, and triple bonds. Covalent bonds involve sharing of electrons and are stronger, while hydrogen bonds are intermolecular forces and thus weaker in nature.

Ammonia is synthesized industrially by the Haber process, which combines nitrogen and hydrogen gases under high temperature and pressure in the presence of a catalyst. The other options are unrelated to ammonia synthesis.

Charles' Law states that the volume of a given amount of gas held at constant pressure is directly proportional to its Kelvin temperature. This means as temperature increases, volume increases proportionally, provided pressure remains constant.

Heating mercuric oxide powder causes it to decompose into mercury and oxygen, which is a chemical change. The other options involve physical changes or no chemical change.