Chemistry MCQs

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The electrons in the outermost occupied shell (or shells) determine the chemical properties of the atom; it is called the valence shell. Each shell consists of one or more subshells, and each subshell consists of one or more atomic orbitals.

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An exothermic reaction is a chemical reaction that releases energy through light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation: reactants – products + energy. Exothermic Reaction means “exo” meaning releases and “thermic” means heat.

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Minamata disease is a poisoning disease that affects mainly the central nervous system and is caused by the consumption of large quantities of fish and shellfish living in Minamata Bay and its surroundings, the major causative agent being some sort of organic mercury compound.

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Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid.

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Solutions that contain ions are good conductors of electricity, such as, acids, bases, salt water. Tap water, lemon juice and mercury is the best liquid conductor compare with others. Because of any solution to conduct, you need ions or free electrons.

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Galvanization is the process of applying a protective zinc coating to steel or iron. It is done to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged in a bath of molten zinc.

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A pearl is largely made of calcium carbonate, CaCO3, and that compound occurs mostly as platelets having the structure of a naturally-occurring mineral called aragonite.

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• Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (such as aluminum, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon.
• Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties.
• Steel is an alloy of iron and carbon in which the carbon content ranges up to 2 percent.
• Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a blue-silvery appearance.

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The reason that it is paramagnetic is because the oxygen molecule has two unpaired electrons. Electrons not only go around the atom in their orbitals, they also spin, which creates a magnetic field. Unpaired electrons spin in the same direction as each other, which increases the magnetic field effect.

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Aufbau principle states that ‘in the ground state of the atom, the orbitals are filled in order of their increasing energies, starting with the orbital of lowest energy.’ The word aufbau is German word which means building up. The increasing order of energy and hence that of filling of orbitals is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.