Chemistry MCQs

Notes:
Potassium permanganate is a point-of-entry treatment method that oxidizes dissolved iron, manganese, and hydrogen sulfide into solid particles that are filtered out of the water. It can also be used to control iron bacteria growth in wells.

Notes:
Oxalic acid is an organic compound with the formula C₂H₂O₄. Some call it “crab acid” due to its appearance. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid.

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Rayon is considered a semi-synthetic fiber. It is made by regenerating natural materials into a usable form. Rayon fibers are derived from cellulose obtained from wood or related agricultural products. It was first commercially produced in 1905 by the Swiss firm J. R. Geigy, originally under the name “artificial silk”

Notes:
Adsorption, the binding of gas or liquid particles to a solid surface, is often used in chromatography – a laboratory technique for the separation of a mixture. This process is critical as it allows the separation of the compounds in the mixture, thereby enabling further analysis or purification. Apart from chromatography, adsorption is also used in scrubbers and purification of solids and liquids.

Notes:
The correct answer is CaO (calcium oxide), which is also known as quicklime. When CaO is dissolved in water, it reacts exothermically to form calcium hydroxide (Ca(OH)2), producing a hissing sound due to the rapid release of heat and steam. This reaction is a classic example of a vigorous exothermic reaction in chemistry. Calcium oxide is commonly used in construction and as a drying agent.

Notes:
L.P.G. (Liquefied Petroleum Gas) primarily consists of propane and butane. It is used as fuel for heating, cooking, and vehicles. Propane (C3H8) and butane (C4H10) are both byproducts of natural gas processing and petroleum refining. LPG is favored for its high energy content and clean-burning properties.

Notes:
Carbon monoxide is colourless, odourless, and tasteless, but highly toxic because it combines with haemoglobin to produce carboxyhemoglobin, which usurps the space in haemoglobin that normally carries oxygen, but is ineffective for delivering oxygen to bodily tissues. Concentrations as low as 667 ppm may cause up to 50% of the body’s hemoglobin to convert to carboxyhemoglobin. The impact is irreversible and that is why that even after available of oxygen, the carboxyhemoglobin does not allow the Oxygen to be taken up.

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Leaching is used for ore concentration if the ore is soluble in some suitable solvent. For example: Leaching of alumina from bauxite using conc. NaOH.

Notes:
The general formula is that the nth shell can hold up to 2n² electrons. For example: for L shell n =2, so maximum number of electrons will be 2(2²) i.e. 8.

Notes:
Manganese is placed in the 7th group and 4th period of the modern periodic table. Its Atomic number is 25 and is placed group VII A.