Chemistry MCQs

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Kohlrausch law of independent migration of ions states that limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte.

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There is a steady increase in boiling point with the increase in molecular mass. This is due to the fact that the intermolecular van der Waals forces increase with increase of the molecular size or the surface area of the molecule.

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Octane number, also known as octane rating, are based on a scale on which iso-octane is 100, which means minimal knock, and heptane is 0. The higher the octane number, the more compression required for fuel ignition.

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A Thermosetting polymer can be heated only once when it permanently sets into a solid which can not be remelted and remoulded. The thermosetting plastic is cross linked and is permanently rigid. The common example are bakelite, melamine, formaldehyde resin, etc. Teflon is a thermoplastic.

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Lustrous means shiny or gleaming. Most nonmetals do not have a shiny appearance. However, iodine is an exception. Iodine is a nonmetal that appears lustrous or metallic. It has a shiny, metallic luster in its solid state due to its large number of delocalized electrons. This is a rare characteristic for nonmetals and iodine and carbon are examples of very few exceptions.

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White phosphorus finds its use in various military applications such as incendiary bombs, for smoke-screening as smoke pots and smoke bombs, and in tracer ammunition.

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Sulphur is commonly used in fire-crackers. Nitrogen and Phosphorous are two other non-metals which are commonly used in fireworks.

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“Dry ice” is solid carbon dioxide (CO2). Carbon dioxide freezes at -78.5 degrees Centigrade. When dry ice “melts” it undergoes a process called sublimation. This means that it is converted from a solid directly to a gas, bypassing the intermediate liquid stage. This is where the name “dry ice” comes from – when it melts, you never get any liquid, hence it’s “dry”.

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Cadmium poisoning can also cause softening of the bones and kidney failure. The cadmium was released into rivers by mining companies in the mountains, which were successfully sued for the damage. Itai-itai disease is known as one of the 4 Big Pollution Diseases of Japan.

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The Davy lamp is a safety lamp for use in flammable atmospheres, invented in 1815 by Sir Humphry Davy. It consists of a wick lamp with the flame enclosed inside a mesh screen.