Chemistry MCQs

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Aluminum powder is a highly flammable powder produced by grinding aluminum into fine grains of material. Aluminium powder is used to reduce iron oxide in aluminothermy process to produce iron (molten) for welding. Piece of magnesium are used to charge toe mixture.

• Fe2O3 + 2Al —> Al2O3 + 2Fe

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Nitrogen, phosphorus and potassium (NPK) are the three most common bases of fertilizers. Potash can be used to make potassium (K) fertilizers. All commercial potash deposits come originally from marine deposits and are often buried deep in the earth.

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The iron displaces copper from its salt, to make iron sulfate solution and deposit a thin coating of metallic copper on the surface of the metal. In general, any metal higher than copper in the “electromotive series” will displace copper from copper sulfate solution or any other copper salt solution.

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The main gases responsible for causing acid rain are sulphur dioxide as well as nitrous oxides. The main sources of sulphur dioxide are metal working industries and coal-fired power stations whereas nitrous oxide is from vehicles and fuel combustion.

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In order to make the image permanent, it is necessary to remove the unreduced silver bromide from the surface of the developed film. This operation is called fixing of image. Fixing is done by dipping the developed film or plate in sodium thiosulphate (hypo) solution. The hypo solution dissolves the unreduced silver bromide by forming a complex. Thus, sodium thiosulphate acts as a complexing agent.

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The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). Also known as inert gases, they make up a group of chemical elements with similar properties; under standard conditions, they are all odourless, colourless, monatomic gases with very low chemical reactivity.

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A reactive metal is one that readily reacts with other elements to give up its electrons. The order of intensity of reactivity is known as reactivity series. Potassium is at the top of the series and hence most reactive. Reactivity of some metals are given in descending order:

• K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu

Notes:
Rose’s metal is an alloy of bronze, bismuth, lead and tin. It consists of 50% bismuth, 25–28% lead and 22–25% tin. It is a fusible alloy with a low melting point. It was discovered by the German chemist Valentin Rose the Elder, the grandfather of Heinrich Rose.

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Cement (e.g., Portland cement) hardens because of hydration a chemical reaction that occurs independently with the mixture’s water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble.

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Fiber glass is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK. Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals. Common uses of fiberglass include high performance aircrafts (gliders), boats, automobiles, baths, hot tubs, water tanks, roofing, pipes, cladding, casts, Surfboards, and external door skins.