Chemistry MCQs

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Antoine Lavoisier was a French nobleman and chemist who was central to the 18th-century chemical revolution and who had a large influence on both the history of chemistry and the history of biology. He is widely considered in popular literature as the “father of modern chemistry”. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen and hydrogen.

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Microcapsules are composed of lipids, proteins and polysaccharides. This material is widely used, especially for walls and other structure. Such as gelatin, ethyl cellulose, etc.

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Iodoform is the organoiodine compound with the formula CHI3. A pale yellow, crystalline, volatile substance, it has a penetrating odor and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant. Adolf Hitler’s mother, Klara Hitler, died of iodoform poisoning brought on by her treatment for breast cancer.

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Atoms that have the same number of protons but different numbers of neutrons are called isotopes. Therefore, they have same atomic number while differ in mass number. Such as in C-12 and C-14.

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Electrons move around the nucleus in orbital motion. Such as motion involves the quantum mechanical motion of rigid particles (electrons in this case) about some other mass, or about themselves. Orbital motion involves translation of the center of mass rather than spin (rotation about the axis). Traditional physicists compare the movement of electrons as analogous to that of planetary motion around the sun.

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J. J. Thomson discovered a negatively charged particle, called the electron. The alpha particle is nothing but positively charged helium nuclei, it has charge of two time of that of the proton, as it is constituted of two protons.

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Ice is not a mixture because the atoms in the ice are locked in a crystalline matrix whose atoms are less densely packed than those in the liquid water, a unique property of water.

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An electron shell, or a principal energy level, may be thought of as an orbit followed by electrons around an atom’s nucleus. Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.

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A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light. There are two varieties of such lamps: low pressure and high pressure. Low-pressure sodium lamps are the most efficient electrical light sources, but their yellow light restricts applications to outdoor lighting such as street lamps. High-pressure sodium lamps have a broader spectrum of light but poorer colour rendering than other types.

Notes:
Aerated water is, correctly speaking, water to which air is added. So aerated water is any water artificially impregnated with a large amount of gas (carbon dioxide). The term is, however, frequently applied to carbonated water.

• H2O + CO2 —> H2OC3