Chemistry MCQs

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A high-refractive-index polymer is a polymer that has a refractive index greater than 1.50. Such materials are required for anti-reflective coating and photonic devices such as light emitting diodes (LEDs) and image sensors.

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Bakelite is a thermosetting plastic formed from phenol and formaldehyde, used in electrical insulators and cookware handles. Unlike thermoplastics, it hardens irreversibly when heated and cannot be remolded. It was the first synthetic plastic, invented by Leo Baekeland in 1907.

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Rayon is the first man-made fiber, also known as “artificial silk”. It was developed in the late 19th century as a substitute for natural silk. Rayon is a semi-synthetic fiber made from wood pulp. It has properties similar to silk and a shiny appearance.  Nylon is the first fully synthetic fiber. It is made from coal, water, and air. Nylon is strong, elastic, and easy to wash. It is used to make socks, ropes, tents, and more.

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Polycarbonate(PC) is a tough thermoplastic. It is not only highly transparent but also has good toughness which most of the other thermoplastics do not possess. For this reason, it is widely used for making CDs, Safety Goggles, Mixer jar lids etc.

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Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 k) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.
 In the manufacture of tyre rubber, 5% of sulphur is used as a crosslinking agent

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MTBE is a gasoline additive, used as an oxygenate to raise the octane number. Its use is controversial in the US and declining in that country in part because of its occurrence in groundwater and legislation favoring ethanol.

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Allotropes refer to two or more different physical forms in which an element can exist. The property is due to different ways atoms bond together. The most common instance is the element carbon, which exists in several different forms, including diamond, graphite, and fullerenes, making it an allotropic element. It’s crucial to note that allotropy applies to elements, not compounds.

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Cinnabar, also known as mercurblende, is indeed the most common ore source for refining elemental mercury. However, its color range runs from scarlet to brick-red, not grey to green. It is known for providing the brilliant red or scarlet pigment known as vermilion, not a blue pigment.

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Electronegativity is defined as an atom’s ability to attract an electron pair when forming a covalent bond. This property increases as you move left to right across the periodic table due to an increase in the nuclear charge’s attractive forces. It decreases as you move top to bottom, owing to the shielding effect of sub-levels and increased atomic radius, which makes electrons easier to remove. This culminates in Fluorine, being the highest and furthest to the right on the periodic table, hence it is the most electronegative.

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The correct statement is that in an alkaline battery, the negative terminal is made of zinc powder, the positive terminal is made of manganese dioxide, and the electrolyte is potassium hydroxide (KOH). Alkaline batteries are known for their long shelf life and higher energy density compared to zinc-carbon batteries. They were invented in the 1950s and are widely used in household devices.