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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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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Brass is an alloy of Copper and Zinc, in proportions which can be varied to achieve varying mechanical and electrical properties. The proportions of Zinc and Copper can vary to create different types of brass alloys with varying mechanical and electrical properties.

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Polyvinyl chloride (PVC) is made from the monomer vinyl chloride (CH2 =CHCl). It is used for making raincoats, handbags, toys including dolls, electrical goods and as a covering of electrical wires.

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Nitrolim is a type of fertilizer that was widely used in the past. The main components of Nitrolim are calcium carbide and nitrogen. Calcium carbide reacts with nitrogen to form calcium cyanamide, which is an active ingredient in Nitrolim. This fertilizer is significant as it helps in fixing nitrogen in the soil thereby promoting plant growth.

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Water at 4 degrees Celsius has maximum density. This is due to the unique molecular structure of water, which allows it to reach its highest density at this temperature. As water cools from higher temperatures, it becomes denser until it reaches 4 degrees. below this temperature, it begins to expand, making ice less dense than liquid water. This phenomenon is crucial for aquatic life, as it allows ice to float, insulating the water below.

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Alcohols are organic compounds characterized by the presence of a hydroxyl group, denoted as -OH. This group consists of one oxygen atom bonded to a hydrogen atom. Due to the presence of the hydroxyl group, alcohols exhibit unique properties, such as the ability to form hydrogen bonds, making them polar. Alcohols are distinct from carboxylic acids (COOH), carbonates (COO), and carbonyl group compounds (CO).

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Gun metal is an alloy primarily composed of copper, tin, and zinc. Specifically, it typically contains about 88% copper, 10% tin, and 2% zinc. This alloy is known for its strength, corrosion resistance, and ability to withstand high temperatures, making it ideal for manufacturing firearms and artillery. The term “gun metal” dates back to the 15th century when it was used for cannons and other weaponry.

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Silica gel possesses hygroscopic properties, meaning it can absorb and hold water vapour. This makes it an effective desiccant or drying agent. When packaged with products, silica gel can help control humidity and prevent spoilage or degradation by absorbing excess moisture. This property is particularly valuable when shipping or storing items that can be negatively impacted by damp conditions, like electronics, food, and leather goods.

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Carbon exhibits many allotropic forms; both crystalline as well as amorphous. Diamond and graphite are two well-known crystalline forms of carbon. In 1985, third form of carbon known as fullerenes was discovered.