Chemistry MCQs

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Silver is best conductor of heat while among metals lead is poorest conductor of heat. Cooper and aluminum are good conductor while mercury is a poor conductor.

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Nitrolim is a type of fertilizer that was widely used in the past. The main components of Nitrolim are calcium carbide and nitrogen. Calcium carbide reacts with nitrogen to form calcium cyanamide, which is an active ingredient in Nitrolim. This fertilizer is significant as it helps in fixing nitrogen in the soil thereby promoting plant growth.

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In an electrochemical cell, the half cell where oxidation takes place is known as oxidation half cell and the half cell where reduction takes place is known as reduction half cell. Oxidation takes place at anode which is negatively charged and reduction takes place at cathode which is positively charged.

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Flint is a sedimentary rock. It’s a type of microcrystalline quartz in the chert family. Flint is known for its sharp edges and ability to be easily flaked into various shapes. It was widely used by early humans to make a variety of tools, including:  Knives, Scrapers, Points, Axe-heads, Hammers, Choppers. Flint is often found along streams and beaches. It’s close behind diamond in hardness and fractures easily to give razor sharp edges.

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Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2. However, hydrogen gas is very rare in the Earth’s atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth’s gravity more easily than heavier gases. However, hydrogen is the third most abundant element on the Earth’s surface, mostly in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus, as is methane, itself a hydrogen source of increasing importance.

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The adsorption of hydrogen by palladium is called occlusion. Occlusion is a type of adsorption where gases are adsorbed onto metals. The hydrogen adsorbed onto palladium is called occluded hydrogen.
Palladium can absorb about 900 times its own volume of hydrogen. The hydrogen that is adsorbed is more active than normal hydrogen.
The adsorption of hydrogen on palladium occurs through a hydride formation. The chemical bonds that are formed cannot be broken easily to release the hydrogen gas from the surface of the metal.
The process of occlusion is used to purify hydrogen.

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Tear gas is also known as CS Gas. It acts as a lachrymatory agent. Tear gas irritate the mucous membrane of the eyes, nose, mouth and lungs, and causes tearing, coughing, burning and difficult breathing.

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Graphene oxide is used as a molecular sieve to filter common salts from seawater to produce potable water.

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Plaster of Paris is the common name of calcium sulphate hemihydrate because half molecule of water is attached with calcium sulphate. The chemical formula of plaster of Paris is CaSO₄.1/2H₂O.

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The cells are called Direct-formic acid fuel cells, in which formic acid is directly fed in the cells. Storage of formic acid is much easier and safer than that of hydrogen because it does not need to be done at high pressures and (or) low temperatures, as formic acid is a liquid at standard temperature and pressure. Formic acid does not cross over the polymer membrane, so its efficiency can be higher than that of methanol. Use of acetic acid in cells does not arise.