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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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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Noble gases are characterized by their low reactivity. The reason for this is their full electron shell, which makes them very stable and unlikely to engage in chemical reactions. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). Despite the inertness of noble gases, some of them like Xenon are known to form compounds.

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When sulfuric, and nitric acids, present in the acid rain reacts with the calcite in marble and limestone, it get dissolve and formed gypsum and washed off by the water. The rain can dissolve limestone and marble through direct contact.

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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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Adding washing soda (sodium carbonate) can remove both temporary and permanent hardness from water. Washing soda reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates.

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Nerve agents are a class of phosphorus containing organic compounds.

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Linear strain: If the deforming force produces a change in length alone, the strain produced in the body is called linear strain or tensile strain. Linear strain in the direction of deforming force is called longitudinal strain and in a direction perpendicular to force is called lateral strain.

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The alkaline earth metals have low ionization enthalpies due to fairly large size of the atoms. Since the atomic size increases down the group, their ionization enthalpy decreases.