Chemistry MCQs

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Methanol (CH₃OH) is also known as Wood Alcohol. It’s a solvent in many chemical processes and is a component of automobile antifreeze.

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The noble gases are the chemical elements in group 18 of the periodic table. They are the most stable due to having the maximum number of valence electrons their outer shell can hold. This chemical series contains helium, neon, argon, krypton, xenon, and radon.

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Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. When oxidation occurs, an element loses electrons and its oxidation number increases .i.e. it becomes more positive.

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The given principle is one of the postulates of the Dalton’s atomic theory given in 1803 by John Dalton. The postulates of Dalton’s atomic theory are as follows: 
1. Elements consist of indivisible small particles (atoms). 
2. All atoms of the same element are identical; different elements have different types of atom. 
3. Atoms can neither be created nor destroyed. 
4. ‘Compound elements’ (i.e. Compounds) are formed when atoms of different elements join in simple ratios to form ‘compound atoms’ (i.e. Molecules).

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Sodium sulfate, used as a filler in detergent powder, enables the adjustment of the concentration of the active matter in the detergent, as required.

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Allotropes refer to two or more different physical forms in which an element can exist. The property is due to different ways atoms bond together. The most common instance is the element carbon, which exists in several different forms, including diamond, graphite, and fullerenes, making it an allotropic element. It’s crucial to note that allotropy applies to elements, not compounds.

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Electronegativity is defined as an atom’s ability to attract an electron pair when forming a covalent bond. This property increases as you move left to right across the periodic table due to an increase in the nuclear charge’s attractive forces. It decreases as you move top to bottom, owing to the shielding effect of sub-levels and increased atomic radius, which makes electrons easier to remove. This culminates in Fluorine, being the highest and furthest to the right on the periodic table, hence it is the most electronegative.

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The correct answer is Technetium. It has the atomic number 43 and is the lowest atomic number element without any stable isotopes. All of its isotopes are radioactive, with Technetium-98 being the most stable, having a half-life of about 4.2 million years. Technetium was first artificially produced in 1937 by Carlo Perrier and Emilio Segrè, making it the first element to be artificially created.

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Third option is the correct answer
Photochemical smog is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone.

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One of the most important chemical components of the troposphere is the ‘hydroxyl radical’: a highly reactive substance composed of an oxygen and a hydrogen atom, denoted ‘OH’. Hydroxyl radicals react with just about any other trace gas they encounter, removing them from the atmosphere.For example, OH combines with toxic carbon monoxide to generate carbon dioxide. In this sense, OH ‘cleans up’ the troposphere, and is sometimes called the detergent of the atmosphere.