Chemistry MCQs

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Alkali metals have one electron in their valence shell and hence they easily lose or donate electron.

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Sodium thiosulfate is an important inorganic salt with several medical uses. It is also called sodium hyposulfite or ‘hypo’. It is used in several pharmaceutical preparations and also has various medical properties. 

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Graphite is renowned for its conspicuous uses owing to its unique properties like its ability to conduct electricity, which makes it ideal for electrode manufacturing. It’s also used as a lubricant and in the production of crucibles, thanks to its high melting point. However, it isn’t used in glass cutting.

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Cobalt Oxide is commonly used to create a distinctive blue hue in glasses and ceramics. The depth of the blue can be altered by changing the concentration of the oxide. In addition to being used for aesthetic purposes, Cobalt blue, which results from Cobalt Oxide, is also used because it absorbs certain wavelengths of light, making it useful for filtering out unwanted wavelengths.

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The electric heating is also used to produce light, as in an electric bulb. Here, the filament must retain as much of the heat generated as is possible, so that it gets very hot and emits light. It must not melt at such high temperature. A strong metal with high melting point such as tungsten (melting point 3380°C) is used for making bulb filaments. The filament should be thermally isolated as much as possible, using insulating support, etc. The bulbs are usually filled with chemically inactive nitrogen and argon gases to prolong the life of filament. Most of the power consumed by the filament appears as heat, but a small part of it is in the form of light radiated.

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In 17 carat gold, the composition is 17 parts gold and 7 parts other metals, making it 70.6% gold. The term “carat” refers to the purity of gold, with 24 carats being pure gold. Thus, 17 carat gold contains 7 parts of other metals, which can include copper, silver, or palladium, used to enhance durability and alter color.

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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.

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The correct answer is Octaoxygen. Octaoxygen (O8) is an allotrope of oxygen that can exist in multiple phases under varying pressures and temperatures. It was first synthesized in 2001 and is notable for its unique molecular structure, which consists of eight oxygen atoms. Ozone (O3) is well-known but does not exhibit multiple phases like octaoxygen. Tetraoxygen (O4) is less stable and not commonly referenced in the same context.

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Aluminum is considered a “Green Metal” primarily due to its high recycling rate. Approximately 75% of all aluminum ever produced is still in use today, as it can be recycled indefinitely without losing quality. This process saves energy—recycling aluminum uses about 95% less energy than producing new aluminum from bauxite ore. Additionally, recycling reduces greenhouse gas emissions and conserves natural resources, making aluminum a sustainable choice in various applications.

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Plumbism is also known as lead poisoning or  a condition which occurs when there is accumulation of lead in body, usually over a few months' time period and even years.