Chemistry MCQs

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Fluorine is most active because it has the highest electronegativity.

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Calamine is an ore that contains zinc carbonate along with impurities like iron oxide. Through smelting, the zinc carbonate in calamine can be reduced to extract pure zinc metal. Other common zinc ores are sphalerite (zinc sulfide) and smithsonite (zinc carbonate). So calamine is considered a zinc ore due to its zinc carbonate content.

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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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Andesite is an igneous volcanic rock with intermediate composition and is not used as an ore. Chalcopyrite is a major copper ore, sphalerite is the primary ore of zinc, and cinnabar is the main ore of mercury. Andesite mainly consists of plagioclase, pyroxene, and amphibole minerals and forms in volcanic arcs associated with subduction zones.

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Sodium benzoate is commonly used as a preservative in food and beverages, including tomato juice. It inhibits the growth of mold, yeast, and some bacteria, extending shelf life. It is effective in acidic environments, such as those found in tomato products, where the pH is typically below 4.6. Sodium chloride (salt) can also act as a preservative but is primarily used for flavor. Sodium carbonate and sodium lauryl sulfate are not suitable preservatives for tomato juice.

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The term for the minimum temperature necessary to ignite a combustible substance is “Ignition Temperature”. It plays a critical role in fire safety and in the field of thermodynamics. Incorrect handling of substances with low ignition temperatures can lead to hazardous situations like unexpected fires or explosions. Additionally, understanding a material’s ignition temperature helps in proper storage and safe handling to prevent unwanted accidents.

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The carbon content of Kerosene is higher than the other fuels mentioned in the option, that is why it will emit maximum mass of carbon dioxide, when the same quantity is burnt.

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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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The non-metallic character of elements decreases down the group. In fact, the heaviest element in each p-block group is the most metallic in nature.

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Potassium carbonate is a salt which is white in colour. It is used in the production of soap. Its chemical formula is K₂ CO₃.