Chemistry MCQs

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Krypton is a chemical element with symbol Kr and atomic number 36. It is a member of group 18 (noble gases) elements. The electronic configuration of Krypton is [2, 8, 18, 8]

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Tap water contains ions (due to dissolved impurities) which help in conduction of electricity. Whereas, distilled water does not contain ions, so it can not conduct electricity.

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Democritus first suggested the existence of the atom, but John Dalton (1766-1844) is credited with the Atomic Theory of Matter. According to Dalton, all matter is made of atoms; atoms are indivisible and indestructible; all atoms of a given element are identical in mass and properties; and compounds are formed by a combination of two or more different kinds of atoms.

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In 1905, it was Einstein who suggested the concept of light having a dual nature; particle and wave nature. In a similar way, Louise de Broglie suggested that electron also exhibits a dual nature. Broglie derived a mathematical expression to prove the wave nature of electron along with particle nature. He gave the following relation:- O = h/mv, where O is the wavelength of electron, m is mass of an electron and v is the frequency.

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A heavy, silvery d-block element, Mercury is the only metal that is liquid at STP The only other elements that are liquid under these conditions is bromine.

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The Sun is composed primarily of the chemical elements hydrogen and helium; they account for 74.9% and 23.8% of the mass of the Sun. The presence of helium is because of nuclear fusion reaction of hydrogen in which immense amount of energy is produced.

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The transition metals with d-orbitals have a tendency to lose electrons. Since the electrons in the highest energy level are actually on a lower principal energy number than the ones before them, this makes it relatively easy to lose some or all of their electrons to land in stable state. When these metals form ions, the 4s electrons are always lost first; so, they form only cations (positive ions).

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Chlorine bleaches by the process of oxidation. It needs moisture for its bleaching action. Chlorine reacts with water to form hydrochloric and hypochlorous acids. Hypochlorous acid is unstable, and it easily dissociates to form nascent oxygen.

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Heavy water is made of Deuterium Oxide (2H2O). It is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2H or D), rather than the common hydrogen-1 isotope (1H or H or protium) that makes up most of the hydrogen in normal water.

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Ferrous minerals contain iron, non-ferrous minerals do not contain iron. Iron ore and manganese are two important ferrous minerals. Chromite is also a ferrous mineral; its chemical name is Iron Chromium Oxide, with the chemical formula FeCr2O4. The non-ferrous metallic minerals include the ores of copper, lead and zinc, tin, graphite, tungsten, mercury, etc.