Chemistry

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.

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.

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.

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.

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).

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.

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.

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

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.

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.