Chemistry MCQs

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John Dalton introduced the atomic theory into chemistry. The main points of Dalton’s atomic theory are (1) Elements are made of extremely small particles called atoms. (2) Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.(3) Atoms cannot be subdivided, created or destroyed. (4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. (5) In chemical reactions, atoms are combined, separated or rearranged.

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Radium(Ra) with atomic number 88 was discovered by Marie and Pierre Curie in 1898 as Radium Chloride. However, it was Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911.

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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.

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Cellulose is the most abundant organic compound in nature. It is the main constituent of plant fiber. Plants contain on average 33% cellulose, and cotton is the purest form at 90%. Chitin is the second most abundant organic compound in nature.

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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.

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Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc

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When Mendeleev published his periodic table in 1869, noble gases had not yet been discovered. The first noble gas, argon, was identified in 1894 by Lord Rayleigh and William Ramsay. In contrast, lanthanides and actinides were recognized later, but their existence was inferred from Mendeleev’s predictions. Halogens, including elements like chlorine and iodine, were known prior to Mendeleev’s work.

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Ground Level Ozone results from photochemical reactions between oxides of nitrogen (NO_x) and volatile organic compounds (VOCs) in the presence of sunlight.

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Bleaching powder is made by passing Cl2 into slaked lime. Though bleaching powder is often written as Ca(OCl)₂ , it is really a mixture and not a compound.

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The elements of Group 2 include beryllium, magnesium, calcium, strontium, barium and radium. These elements with the exception of beryllium are commonly known as the alkaline earth metals.