Chemistry GK Questions Quiz-13

Chemistry GK Questions Quiz-13

Chemistry Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Chemistry for competitive examinations.

    241. German silver, an alloy, does not contain the metal

    (1) Nickel 
    (2) Zinc
    (3) Copper 
    (4) Silver
    Answer:
    241. (4) Nickel silver is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. Nickel silver is named for its silvery appearance, but it contains no elemental silver unless plated. The name “German silver” refers to its development by 19th-century German metalworkers in imitation of the Chinese alloy known as paktong (Cupronickel) All modern, commercially important nickel silvers (such as those standardized under ASTM B122) contain significant amounts of zinc, and are sometimes considered a subset of brass. Nickel silver first became popular as a base metal for silver-plated cutlery and other silverware, notably the electroplated wares called EPNS (electro-plated nickel silver). It is used in zippers, better-quality keys, costume jewellery.

    242. Oxygen which is vital for life is a product of photosynthesis and comes from

    (1) carbonates from soil
    (2) carbon dioxide
    (3) water
    (4) oxides of mineral elements
    Answer:
    242. (3) The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. This
    biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs
    on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen
    cycle is photosynthesis, which is responsible for modern Earth’s atmosphere. Photosynthesis releases
    oxygen into the atmosphere, while respiration and decay remove it from the atmosphere. In the present
    equilibrium, production and consumption occur at the same rate of roughly 1/2000th of the entire
    atmospheric oxygen per year. Free oxygen also occurs in solution in the world’s water bodies. The increased solubility of O2 at lower temperatures has important implications for ocean life, as polar oceans support a much higher density of life due to their higher oxygen content.

    243. Detergents are

    (1) Sodium salts of fatty acids
    (2) Sodium salts of sulphonic acids
    (3) Sodium salt of benzoic acid
    (4) None of the above
    Answer:
    243. (2) A detergent is a surfactant or a mixture of surfactants with “cleaning properties in dilute
    solutions.” These substances are usually alkylbenzenesulfonates, a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water. In most household
    contexts, the term detergent by itself refers specifically to laundry detergent or dish detergent, as opposed to hand soap or other types of cleaning agents. Detergents are commonly available as powders or concentrated solutions. Detergents, like soaps, work because they are amphiphilic: partly hydrophilic (polar) and partly hydrophobic (non-polar). Their dual nature facilitates the mixture of hydrophobic compounds (like oil and grease) with water. Because air is not hydrophilic, detergents are also foaming agents to varying degrees.

    244. The noble gas used in radiotherapy is

    (1) neon 
    (2) argon
    (3) radon 
    (4) xenon
    Answer:
    244. (3) An early-20th-century form of quackery was the treatment of maladies in a radiotorium. It was a small, sealed room for patients to be exposed to radon for its “medicinal effects”. The carcinogenic nature of radon due to its ionizing radiation became apparent later on. Radon’s molecule-damaging radioactivity has been used to kill cancerous cells. It does not, however, increase the health of healthy cells. In fact, the ionizing radiation causes the formation of free radicals, which results in genetic and other cell damage, resulting in increased rates of illness, including cancer. Exposure to radon, a process known as radiation hormesis, has been suggested to mitigate auto-immune diseases such as arthritis. As a result, in the late 20th century and early 21st century, “health mines” established in Basin, Montana attracted people seeking relief from health problems such as arthritis through limited exposure to radioactive mine water and radon.

    245. Steel contains

    (1) 0.1 – 2% carbon
    (2) 5 – 10% carbon
    (3) more than 10% carbon
    (4) no carbon
    Answer:
    245. (1) Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

    246. The chemical(s) most commonly used for cloud seeding or ‘artificial rainmaking’ is/are

    (1) Silver Iodide
    (2) Sodium Chloride
    (3) Dry ice or frozen carbon dioxide
    (4) All the above
    Answer:
    246. (1) Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud
    condensation or ice nuclei, which alter the microphysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports. The most common chemicals used for cloud seeding include silver iodide and dry ice (solid carbon dioxide). Liquid propane, which expands into a gas, has also been used. This can produce ice crystals at higher temperatures than silver iodide. The use of hygroscopic materials, such as salt, is becoming more popular after promising research.

    247. The substance that is added to make natural rubber strong and more bouncy is

    (1) Polythene 
    (2) Sponge
    (3) Sulphur 
    (4) Chlorine
    Answer:
    247. (3) Vulcanization is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent “curatives” or “accelerators”. These additives modify the polymer by forming crosslinks (bridges) between individual polymer chains. Vulcanized materials are less sticky and have superior mechanical properties.

    248. White phosphorus is always kept under

    (1) benzene 
    (2) kerosene
    (3) ether 
    (4) water
    Answer:
    248. (4) White phosphorus is a material made from a common allotrope of the chemical element phosphorus that is used in smoke, tracer, illumination and incendiary munitions. Other common names include WP, and the slang term “Willie Pete,” which is dated from its use in Vietnam, and is still sometimes used in military jargon. As an incendiary weapon, white phosphorus burns fiercely and can set cloth, fuel, ammunition and other combustibles on fire, and cause serious burns or death and that is why it is kept in water. In addition to its offensive capabilities, white phosphorus is also a highly efficient smoke-producing agent, burning quickly and causing an instant bank of smoke. As a result, smoke-producing white phosphorus munitions are very common, particularly as smoke grenades for infantry, loaded in grenade launchers on tanks and other armored vehicles, or as part of the ammunition allotment for artillery or mortars.

    249. Galena is a mineral of

    (1) iron 
    (2) gold
    (3) lead 
    (4) calcium
    Answer:
    249. (3) Galena is the natural mineral form of lead (II) sulfide. It is the most important lead ore mineral. Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often associated with the minerals sphalerite, calcite and fluorite. Galena deposits often contain significant amounts of silver as included silver sulfide mineral phases or as limited solid solution within the galena structure. These argentiferousgalenas have long been the most important ore of silver in mining. In addition zinc, cadmium, antimony, arsenic and bismuth also occur in variable amounts in lead ores.

    250. Magnalium is an alloy of

    (1) Aluminium and Magnesium
    (2) Magnesium and Tin
    (3) Aluminium and Zinc
    (4) Manganese and Magnesium
    Answer:
    250. (1) Magnalium is an aluminium alloy with 1.5 to 2% magnesium and small amounts of copper, nickel, and tin. Some alloys, intended for particular uses at the cost of poor corrosion resistance, may consist of up to 50% magnesium. It finds use in engineering and pyrotechnics. Alloys with smaller amounts of magnesium (about 5%) exhibit greater strength, greater corrosion resistance, and lower density than pure aluminium. Such alloys are also more workable and easier to weld than pure aluminium. Alloys with high amounts of magnesium (around 50%) are brittle and more susceptible to corrosion than aluminium. Although they are generally more expensive than aluminium, the high strength, low density, and greater workability of alloys with low amounts of magnesium leads to their use in aircraft and automobile parts.

    251. Galvanization of iron is carried out using

    (1) Zinc 
    (2) Tin
    (3) Copper 
    (4) Chromium
    Answer:
    251. (1) Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani. Although galvanization can be done with electrochemical and electrodeposition processes, the most common method in current use is hot-dip galvanization, in which steel parts are submerged in a bath of molten zinc.

    252. Cokking gas is a mixture of

    (1) methane and ethylene
    (2) carbon dioxide and oxygen
    (3) butane and propane
    (4) carbon monoxide and carbon dioxide
    Answer:
    252. (3) Liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or simply propane or butane, is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles. It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer. When specifically used as a vehicle fuel it is often referred to as autogas. LPG can be used as a power source for combined heat and power technologies (CHP). CHP is the process of generating both electrical power and useful heat from a single fuel source. This technology has allowed LPG to be used not just as fuel for heating and cooking, but also for de-centralised generation of electricity. LPG can be stored in a variety of ways. LPG, as with other fossil fuels, can be combined with renewable power sources to provide greater reliability while still achieving some reduction in CO2 emissions.

    253. Dry powder fire extinguishers contain

    (1) sand
    (2) sand and sodium carbonate
    (3) sand and potassium carbonate
    (4) sand and sodium bicarbonate
    Answer:
    253. (4) Dry chemical is a powder based agent that extinguishes by separating the four parts of the fire
    tetrahedron. It prevents the chemical reactions involving heat, fuel, and oxygen and halts the production of fire sustaining “free-radicals”, thus extinguishing the fire. Sodium bicarbonate, “regular” or “ordinary” used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is, the gas drives oxygen away from the fire, thus stopping the chemical reaction. This agent is not generally effective on class A fires because the agent is expended and the cloud of gas dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires don’t usually store much heat in their fuel source, solid fires do. 

    254. Which type of glass is used for making glass reinforced plastic?

    (1) Pyrex glass 
    (2) Flint glass
    (3) Quartz glass 
    (4) Fibre glass
    Answer:
    254. (4) Fiberglass is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK. Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes. Common uses of fiberglass include high performance aircrafts (gliders), boats, automobiles, baths, hot tubs, water tanks, roofing, pipes, cladding, casts, Surfboards, and external door skins.

    255. Two elements which are used to absorb neutrons to control the chain reaction during nuclear fission are

    (1) Boron and Cadmium
    (2) Boron and Plutonium
    (3) Cadmium and Uranium
    (4) Uranium and Boron
    Answer:
    255. (1) Since the continued chain reaction of a nuclear fission reactor depends upon at least one neutron from each fission being absorbed by another fissionable nucleus, the reaction can be controlled by using control rods of material which absorbs neutrons. Cadmium and boron are strong neutron absorbers and are the most common materials used in control rods. In the operation of a nuclear reactor, fuel assemblies are put into place and then the control rods are slowly lifted until a chain reaction can just be sustained. As the reaction proceeds, the number of uranium-235 nuclei decreases and fission byproducts which absorb neutrons build up. To keep the chain reaction going, the control rods must be
    withdrawn further. At some point, the chain reaction cannot be maintained and the fuel must be replenished.

    256. The most commonly used chemicals in the artificial rainmaking or cloud seeding are

    (1) Silver Iodide (Ag I)
    (2) Sodium Chloride (NaCl)
    (3) Dry Ice (Frozen CO2)
    (4) All of the above
    Answer:
    256. (1) Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud
    condensation or ice nuclei, which alter the microphysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports. The most common chemicals used for cloud seeding include silver iodide and dry ice (solid carbon dioxide). Liquid propane, which expands into a gas, has also been used. This can produce ice crystals at higher temperatures than silver iodide. Seeding of clouds requires that they contain super-cooled liquid water—that is, liquid water colder than zero degrees Celsius. Introduction of a substance such as silver iodide, which has a crystalline structure similar to that of ice, will induce freezing nucleation. The most communly used Chemicals in the artificial rainmaking or cloud seeding are silver Iodide.

    257. Which of the following can be used to absorb neutrons to control the chain reaction during nuclear fission ?

    (1) Boron 
    (2) Heavy water
    (3) Uranium 
    (4) Plutonium
    Answer:
    257. (1) Boron shielding is used as a control for nuclear reactors, taking advantage of its high cross-section for neutron capture. Elemental boron is rare and poorly studied because the material is extremely difficult to prepare. Most studies on “boron” involve samples that contain small amounts of carbon. Chemically, boron behaves more similarly to silicon than to aluminium. Crystalline boron is chemically inert and resistant to attack by boiling hydrofluoric or hydrochloric acid. When finely divided, it is attacked slowly by hot concentrated hydrogen peroxide, hot concentrated nitric acid, hot sulfuric acid or hot mixture of sulfuric and chromic acids. The rate of oxidation of boron depends upon the crystallinity, particle size, purity and temperature. Boron does not react with air at room temperature, but at higher temperatures it burns to form boron trioxide.

    258. Hydrogen bomb is based on the principle of

    (1) controlled fission reaction
    (2) uncontrolled fission reaction
    (3) controlled fusion reaction
    (4) uncontrolled fusion reaction
    Answer:
    258. (4) A thermonuclear weapon is a nuclear weapon design that uses the heat generated by a fission bomb to compress a nuclear fusion stage which indirectly results in greatly increased energy yield (i.e., bomb “power”). It is colloquially referred to as a hydrogen bomb or H-bomb because it employs hydrogen fusion, though in most applications the majority of its destructive energy comes from uranium fission, not hydrogen fusion by itself. The fusion stage in such weapons is required to efficiently cause the large quantities of fission characteristic of most thermonuclear weapons. The concept of the
    thermonuclear weapon was first developed and used by the United States and has since been used in most of the world’s nuclear weapons.

    259. Supersonic jet causes pollution by thinning of

    (1) O3 layer 
    (2) O2 layer
    (3) SO2 layer 
    (4) CO2 layer
    Answer:
    259. (1) Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing an ultraviolet photon whose wavelength is shorter than 240 nm. This converts a single O2 into two atomic oxygen radicals. The atomic oxygen radicals then combine with separate O2 molecules to create two O
    3 molecules. These ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process which terminates when an oxygen atom
    “recombines” with an ozone molecule to make two O2 molecules.

    260. Which type of glass is used for making glass reinforced plastic?

    (1) Pyrex glass 
    (2) Flint glass
    (3) Quartz glass 
    (4) Fibre glass
    Answer:
    260. (4) Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes.


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