Chemistry GK Questions Quiz-12

Chemistry GK Questions Quiz-12

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

    221. The process of removing calcium and magnesium from hard water is known as

    (1) Sedimentation
    (2) Filtration
    (3) Flocculation
    (4) Water softening
    Answer:
    221. (4) Water softening is the reduction of the concentration of calcium, magnesium, and certain other metal cations in hard water. Hardness ions dissolved in water can cause a variety of undesired effects including interfering with the action of soaps, the buildup of limescale, which can foul plumbing, and galvanic corrosion. Conventional water-softening appliances intended for household use depend on an ion-exchange resin in which hardness ions are exchanged for sodium ions. Water softening may be desirable where the source of water is hard. However, hard water also conveys some benefits to health by reducing the solubility of potentially toxic metal ions such as lead and copper.

    222. The tip of the match-stick contains

    (1) phosphorus pentoxide
    (2) white phosphorus
    (3) red phosphorus
    (4) phosphorus trichloride
    Answer:
    222. (3) A typical modern match is made of a small wooden stick or stiff paper. One end is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. Matches are usually sold in quantity; wooden ones are packaged in boxes, and paper matches are clustered in rows stapled into matchbooks. They are commonly sold by tobacconists and many other kinds of shops. The coated end of a match, known as the match “head,” contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder. There are two main types of matches: safety matches, which can be struck only against a specially prepared surface, and strike-anywhere matches, for which any suitably frictional surface can be used. Some match-like compositions, known as electric matches, are ignited electrically and do not make use of heat from friction. The tip of the match-stick contains red phosphorus.

    223. Match the sourc in Column B with the product of Column A.

    Column A  (Product) 
    (a) Formic acid 
    (b) Citric acid 
    (c) Tartaric acid 
    Column B (Source)
    (1) Lemon
    (2) Tamarind
    (3) Ants
    a b c
    (1) 3 2 1
    (2) 3 1 2
    (3) 2 3 1
    (4) 2 1 3
    Answer:
    223. (2) Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee
    and ant stings. Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks. Citric acid exists in greater than trace amounts in a variety of fruits and vegetables, most notably citrus fruits. Lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits. Tartaric acid is a white crystalline diprotic organic acid. It occurs naturally in many plants, particularly grapes, bananas, and tamarinds, is commonly combined with baking soda to function as a an antioxidant.

    224. Commercially, sodium bicarbonate is known as

    (1) Washing soda
    (2) Baking soda
    (3) Bleaching powder
    (4) Soda ash
    Answer:
    224. (2) Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs. Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, and bicarbonate of soda. In colloquial usage, its name is shortened to sodium bicarb, bicarb soda, or simply bicarb. The word saleratus, from Latin salæratus meaning aerated salt, was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate. The term has now fallen out of common usage.

    225. An emulsifier is an agent which

    (1) stabilises an emulsion
    (2) aids the flocculation of an emulsion
    (3) accelerates the dispersion
    (4) homogenises an emulsion
    Answer:
    225. (1) An emulsifier is a substance that stabilizes an emulsion by increasing its kinetic stability. One class of emulsifiers is known as “surface active substances”, or surfactants. Many different emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions. Common examples include emulsifying wax, cetearyl alcohol, polysorbate 20, and ceteareth 20. Sometimes the inner phase itself can act as an emulsifier, and the result is a nanoemulsion, where the inner state disperses into “nano-size” droplets within the outer phase. A well-known example of this phenomenon, the “Ouzo effect”, happens when water is poured into a strong alcoholic anise-based beverage, such as ouzo, pastis, arak, or raki. The anisolic compounds, which are soluble in ethanol, then form nano-size droplets and emulsify within the water. The resulting colour of the drink is opaque and milky white.

    226. Mortar is a mixture of water, sand and

    (1) Slaked lime 
    (2) Quick lime
    (3) Limestone 
    (4) Gypsum
    Answer:
    226. (1) Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder such as cement or lime (slaked), and water. Mortar can also be used to fix, or point, masonry when the original mortar has washed away. An international team headed by ÅboAkademi University has developed a method of determining the age of mortar using radiocarbon dating. As the mortar hardens, the current
    atmosphere is encased in the mortar and thus provides a sample for analysis. One major challenge is various factors that affect the sample and raise the margin of error for the analysis.

    227. Which of the following substance is highly plastic ?

    (1) Quartz 
    (2) Mica
    (3) Granite 
    (4) Clay
    Answer:
    227. (4) Clays exhibit plasticity when mixed with water in certain proportions. When dry, clay becomes firm and when fired in a kiln, permanent physical and chemical changes occur. These reactions, among other changes, cause the clay to be converted into a ceramic material. Because of these properties, clay is used for making pottery items, both utilitarian and decorative. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered the useful properties of clay. Some of the earliest pottery shards recovered are from central Honshu, Japan. Clay tablets were used as the first known writing medium, inscribed with cuneiform script through the use of a blunt reed called a stylus. Purpose-made clay balls were also used as sling ammunition.

    228. The National Chemical Laboratory (India) is located in

    (1) Mumbai 
    (2) Bangaluru
    (3) Hyderabad
    (4) Pune
    Answer:
    228. (4) NCL, India is a research, development and consulting organization with a focus on chemistry and chemical engineering. It has a successful record of research partnership with industryand is located in pune. NCL belongs to the family of Council of Scientific and Industrial Research (CSIR), the largest chain of public funded research organization in world. NCL’s human resources comprise of over 1000 people of whom 350 are scientist, 110 are technical staff with advanced degrees in science, technology or engineering. Over 400+ students pursue their doctoral research leading to Ph.D degree. Over 400+ research papers in international journals. Over 70+ Indian and foreign patents granted to NCL

    229. Aspirin is common name of

    (1) Salicylic Acid
    (2) Salicylate
    (3) Methyl Salicylate
    (4) Acetyl Salicylic Acid
    Answer:
    229. (4) Aspirin (USAN), also known as acetylsalicylic acid, is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. Aspirin was first isolated by Felix Hoffmann, a chemist with the German company Bayer in 1897. Aspirin also has an antiplatelet effect by inhibiting the production of thromboxane, which under normal circumstances binds platelet molecules together to create a patch over damaged walls of blood vessels. Because the platelet patch can become too large and also block blood flow, locally and downstream, aspirin is also used long-term, at low doses, to help prevent heart attacks, strokes, and blood clot formation in people at high risk of developing blood clots. Aspirin may be effective at preventing certain types of cancer, particularly colourectal cancer.

    230. Carbon monoxide is an inflammable gas. Which one of the following is also inflammable?

    (1) Helium 
    (2) Nitrogen
    (3) Oxygen 
    (4) Hydrogen
    Answer:
    230. (4) At standard temperature and pressure, hydrogen is a colourless, odorless, tasteless, non-toxic,
    nonmetallic, highly combustible diatomic gas with the molecular formula H2. Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds. Hydrogen plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules. Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion for hydrogen is - 286 kJ/mol. Pure hydrogen-oxygen flames emit ultraviolet light and are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine compared to the highly visible plume of a Space Shuttle Solid Rocket Booster.

    231. Which one of the following metals does not react with water to produce Hydrogen ?

    (1) Potassium
    (2) Cadmium
    (3) Sodium 
    (4) Lithium
    Answer:
    231. (2) Cadmium is a soft, malleable, ductile, bluish-white divalent metal. It is similar in many respects to zinc but forms complex compounds. Unlike other metals, cadmium is resistant to corrosion and as a result it is used as a protective layer when deposited on other metals. As a bulk metal, cadmium is insoluble in water and is not flammable; however, in its powdered form it may burn and release toxic fumes. Cadmium occurs as a minor component in most zinc ores and therefore is a byproduct of zinc production. It was used for a long time as a pigment and for corrosion resistant
    plating on steel while cadmium compounds were used to stabilize plastic. With the exception of its use in nickel–cadmium batteries and cadmium telluride solar panels, the use of cadmium is generally decreasing. These declines have been due to competing technologies, cadmium’s toxicity in certain forms and concentration and resulting regulations.

    232. Ozone consists of

    (1) Oxygen only
    (2) Oxygen and Nitrogen
    (3) Hydrogen and Carbon
    (4) Oxygen and Carbon
    Answer:
    232. (1) Ozone (O3), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope (O2), breaking down with a half life of roughly 30 minutes in the lower atmosphere, to normal dioxygen. Ozone is formed from dioxygenby the action of ultraviolet light and also atmospheric electrical discharges, and is present in low concentrations throughout the Earth’s atmosphere. In total, ozone makes up only 0.6 parts per million of the atmosphere. Ozone’s odor is sharp, reminiscent of chlorine, and detectable by many people at concentrations of as little as 10 parts per billion in air. Ozone’s O3 formula was determined in 1865. The molecule was later proven to have a bent structure and to be diamagnetic. In standard conditions, ozone is a pale blue gas that condenses at progressively cryogenic temperatures to a dark blue liquid and finally a violet-black solid

    233. One of the constituents of tear gas is

    (1) Ethane 
    (2) Ethanol
    (3) Ether 
    (4) Chloropicrin
    Answer:
    233. (4) chloropicrin is a colourless liquid that is insoluble in water, with which it is stable. With a vapor pressure of 24 mm Hg, its volatility is between that of phosgene and mustard gas in persistency, although closer to phosgene because it is related to the compound. Tests have shown that chloropicrin causes humans to shut their eyes involuntarily. Chloropicrin can be absorbed systemically through inhalation, ingestion, and the skin. It is severely irritating to the lungs, eyes, and skin. Because of these properties, chloropicrin can only be delivered in shell form as a chemical weapon. Chloropicrin, today, is used as a fumigant to control pests found in the soil. Although less common, it can be used as a poison for vertebrates, such as rabbits. Chloropicrin is commonly used in combination with other fumigants, such as methyl bromide and sulfuryl fluoride, for increased potency and as a warning agent.

    234. An atomic clock is based on transitions in

    (1) Sodium 
    (2) Caesium
    (3) Magnesium 
    (4) Aluminium
    Answer:
    234. (2) An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS. The principle of operation of an atomic clock is not based on nuclear physics, but rather on atomic physics and using the microwave signal that electrons in atoms emit when they change energy levels. Early atomic clocks were based on masers at room temperature. Currently, the most accurate atomic clocks first cool the atoms to near absolute zero temperature by slowing them with lasers and probing them in atomic fountains in a microwave-filled cavity. The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK. Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET).

    235. Silver halides are used in photographic plates because they are

    (1) oxidised in air
    (2) soluble in hyposolution
    (3) reduced by light
    (4) totally colourless
    Answer:
    235. (3) The light-sensitive chemicals used in photographic film and paper are silver halides. Silver halides are used in photographic film and photographic paper, including graphic art film and paper, where silver halide crystals in gelatin are coated on to a film base, glass or paper substrate. When a silver halide crystal is exposed to light, a sensitivity speck on the surface of the crystal is turned into a small speck of metallic silver (these comprise the invisible or latent image). If the speck of silver contains approximately four or more atoms, it is rendered developable - meaning that it can undergo development which turns the entire crystal into metallic silver. Areas of the emulsion receiving larger amounts of light (reflected from a subject being photographed, for example) undergo the greatest development and therefore results in the highest optical density. Silver halides are also used to make corrective lenses darken when exposed to ultraviolet light.

    236. Tetra ethyle lead (TEL) is

    (1) a catalyst in burning fossil fuel
    (2) an antioxidant
    (3) a reductant
    (4) an antiknock compound
    Answer:
    236. (4) Tetraethyl lead was extensively used as an additive to gasoline, wherein it served as an effective antiknock agent and prevented exhaust valve and seat wear. The use of TEL in gasoline started in the US, while in Europe, alcohol was initially used. The advantages of leaded gasoline — its higher energy content and storage quality — eventually led to a universal switch to leaded fuel. One of the greatest advantages of TEL over other antiknock agents or the use of high-octane blend stocks is the very low concentrations needed. Typical formulations called for 1 part of prepared TEL to 1260 parts untreated gasoline. Competing antiknock agents must be used in greater amounts, often reducing the energy content of the gasoline. TEL is highly soluble in gasoline, ethanol is poorly soluble and that solubility decreases as fuel humidity increases. Over time, droplets and pools of water can form in the fuel system creating a risk of fuel line icing.

    237. The isotope used for the production of atomic energy is

    (1) U-235 
    (2) U-238
    (3) U-234 
    (4) U-236
    Answer:
    237. (1) U235 is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope U238 it is fissile, i.e., it can sustain fission chain reaction. It is the only fissile isotope that is a primordial nuclide or found in significant quantity in nature. If at least one neutron from U235 fission strikes another nucleus and causes it to fission, then the chain reaction will continue. If the reaction will sustain itself, it is said to be critical, and the mass of U235 required to produce the critical condition is said to be a critical mass. A critical chain reaction can be achieved at low concentrations of U235 if the neutrons from fission are moderated to lower their speed, since the probability for fission with slow neutrons is greater. In nuclear reactors, the reaction is slowed down by the addition of control rods which are made of elements such as boron, cadmium, and hafnium which can absorb a large number of neutrons. In nuclear bombs, the reaction is uncontrolled and the large amount of energy released creates a nuclear explosion.

    238. Which of the following is not a nucleon?

    (1) Proton 
    (2) Neutron
    (3) Electron 
    (4) Positron
    Answer:
    238. (4) Nucleon is one of the particles that makes up the atomic nucleus. Each atomic nucleus consists of one or more nucleons, and each atom in turn consists of a cluster of nucleons surrounded by one or more electrons. There are two kinds of nucleon: the neutron and the proton. The mass number of a given atomic isotope is identical to its number of nucleons. Thus the term nucleon number may be used in place of the more common terms mass number or atomic mass number. Until the 1960s, nucleons were thought to be elementary particles, each of which would not then have been made up of smaller parts. Now they are known to be composite particles, made of three quarks bound together by the so-called strong interaction. The interaction between two or more nucleons is called inter-nucleon interactions or nuclear force, which is also ultimately caused by the strong interaction. (Before the discovery of quarks, the term “strong interaction” referred to just inter-nucleon interactions.)

    239. The material used in the manufacture of lead pencil is

    (1) Graphite 
    (2) Lead
    (3) Carbon 
    (4) Mica
    Answer:
    239. (1) Pencils create marks via physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. They are noticeably distinct from pens, which dispense liquid or gel ink that stain the light colour of the paper. Most pencil cores are made of graphite mixed with a clay binder, leaving grey or black marks that can be easily erased. Graphite pencils are used for both writing and drawing, and the result is durable: although writing can usually be removed with an eraser, it is resistant to moisture, most chemicals, ultraviolet radiation and natural aging. Other types of pencil core are less widely used. Charcoal pencils are mainly used by artists for drawing and sketching.

    240. If all bullets could not be removed from gun shot injury of a man, it may cause poisoning by

    (1) Mercury 
    (2) Lead
    (3) Iron 
    (4) Arsenic
    Answer:
    240. (2) Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei. Lead is a highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Exposure to high lead levels can severely damage the brain and kidneys in adults or children and ultimately cause death.


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