Chemistry GK Questions Quiz-6

Chemistry GK Questions Quiz-6

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

    101. Radioactive disintegration of uranium ultimately results in formation of

    (1) radium 
    (2) thorium
    (3) polonium 
    (4) lead
    Answer:
    101. (4) Uranium–lead (U–Pb) dating is one of the oldest and most refined of the radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1–1 percent range. The method relies on two separate decay chains, the uranium series from 238U to 206Pb, with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb, with a half-life of 704 million years. These decay routes occur via a series of alpha (and beta) decays, in which 238U with daughter nuclides undergo eight total alpha and six beta decays whereas 235U with daughters only experience seven alpha and four beta decays. The existence of two ‘parallel’ uranium-lead decay routes (238U to 206Pb and 235U to 207Pb) leads to multiple dating techniques within the overall U–Pb system. The term U–Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’.

    102. Which of the following is used in making smoke bombs?

    (1) Sulphur 
    (2) Phosphorus
    (3) Hydrogen 
    (4) Carbon
    Answer:
    102. (4) A smoke bomb is a firework designed to produce smoke upon ignition. Smoke bombs are useful to military units, airsoft games, paintball games, selfdefense and pranks. The smoke bomb was first created in 1848, by the inventor Robert Yale. He developed 17th century Chinese-style fireworks and later modified the formula to produce more smoke for a longer period of time. Coloured smoke devices use a formula that consists of an oxidizer (typically potassium chlorate, KClO3), a fuel (generally sugar), a moderant (such as sodium bicarbonate) to keep the reaction from getting too hot, and a powdered organic dye. The burning of this mixture evaporates the dye and forces it out of the device, where it condenses in the atmosphere to form a “smoke” of finely dispersed particles. A smoke ball is a hollow, cherry-sized sphere of brightly coloured clay or cardboard filled with a smoke-generating composition that produces a forceful jet of coloured smoke for 10 to 15 seconds.

    103. German silver is an alloy of

    (1) copper, nickel and silver
    (2) silver, copper and aluminium
    (3) zinc, copper and nickel
    (4) zinc, silver and copper
    Answer:
    103. (3) Nickel silver, also known as German silver, Argentan, new silver, nickel brass, albata, alpacca,
    or electrum, 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. It is used in zippers, better-quality keys, costume jewellery, for making musical instruments (e.g., cymbals, saxophones), and is preferred for the track in electrically powered model railway layouts, as its oxide is conductive. It is widely used in the production of coins (e.g. Portuguese escudo and the former GDR marks,). Its industrial and technical uses include marine fittings and plumbing fixtures for its corrosion resistance,
    and heating coils for its high electrical resistance.

    104. A metal is exposed to the atmosphere for sometime. It becomes coated with green carbonate. The metal must be

    (1) silver 
    (2) copper
    (3) aluminium
    (4) zinc
    Answer:
    104. (2) Copper forms a rich variety of compounds with oxidation states +1 and +2, which are often called cuprous and cupric, respectively. It does not react with water, but it slowly reacts with atmospheric oxygen forming a layer of brown-black copper oxide. In contrast to the oxidation of iron by wet air, this oxide layer stops the further, bulk corrosion. A green layer of verdigris (copper carbonate) can often be seen on old copper constructions, such as the Statue of Liberty, the largest copper statue in the world built using repoussé and chasing. Hydrogen sulfides and sulfides react with copper to form various copper sulfides on the surface. In the latter case, the copper corrodes, as is seen when copper is exposed to air containing sulfur compounds. Oxygen-containing ammonia solutions give water-soluble complexes with copper, as do oxygen and hydrochloric acid to form copper chlorides and acidified hydrogen peroxide to form copper(II) salts. Copper(II) chloride and copper
    combine to form copper(I) chloride.

    105. Which of the following pairs of materials serves as electrodes in chargeable batteries commonly used in devices such as torch lights, electric shavers, etc. ?

    (1) Iron and cadmium
    (2) Nickel and cadmium
    (3) Lead peroxide and lead
    (4) Zinc and carbon
    Answer:
    105. (2) A rechargeable battery, storage battery, or accumulator is a type of electrical battery. It comprises one or more electrochemical cells, and is a type of energy accumulator. It is known as a secondary cell because its electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network. Several different combinations of chemicals are commonly used, including: lead–acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer). Rechargeable batteries have lower total cost of use and environmental impact than disposable batteries. Some rechargeable battery types are available in the same sizes as disposable types. Rechargeable batteries have higher initial cost, but can be recharged very cheaply and used many times.

    106. Which of the following is a supercooled liquid ?

    (1) Ice Cream 
    (2) Teflon
    (3) Glass 
    (4) Mercury
    Answer:
    106. (3) Most of us think as glass as a solid material, but it is actually a super cooled liquid. Molecular units have a disordered arrangement yet still have sufficient cohesion that mechanical rigidity is produced. Glass was first made in the Middle East, approximately during the third millennium BC. Early uses were primarily for vessels or decoration. Glass did not come into use for windows until the first century AD, and was made at that time by casting or hand blowing the glass. Today, glass is a highly engineered material with many different varieties and countless uses. There is float glass, annealed glass, wired glass, tempered glass, safety or laminated glass, leaded glass, heat absorbing glass, low e glass, etc. Supercooling is the process of chilling a liquid below its freezing point, without it becoming solid.

    107. Metal are good conductors, because

    (1) they contain free electrons
    (2) the molecules in them are very close to each other
    (3) the molecules in them collide very freely
    (4) they contain reflecting surface
    Answer:
    107. (1) Metals typically consist of close-packed atoms, meaning that the atoms are arranged like closely packed spheres. Two packing motifs are common, one being body-centered cubic wherein each metal atom is surrounded by eight equivalent atoms. The other main motif is face-centered cubic where the metal atoms are surrounded by six neighboring atoms. Several metals adopt both structures, depending on the temperature. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are surrounded by de-localized electrons, which are responsible for the conductivity. The solid thus produced is held together by electrostatic interactions between the ions and the electron cloud, which are called metallic bonds. a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons (see electrical conduction). Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell. Insulators are non-conducting materials with few mobile charges and which support only insignificant electric currents.

    108. The first metal used by a man was

    (1) Copper 
    (2) Silver
    (3) Bronze 
    (4) Brass
    Answer:
    108. (1) Copper occurs naturally as native copper and was known to some of the oldest civilizations on record. It has a history of use that is at least 10,000 years old, and estimates of its discovery place it at 9000 BC in the Middle East; a copper pendant was found in northern Iraq that dates to 8700 BC. There is evidence that gold and meteoric iron (but not iron smelting) were the only metals used by humans before copper. The history of copper metallurgy is thought to have followed the following sequence: 1) cold working of native copper, 2) annealing, 3) smelting, and 4) the lost wax method. In southeastern Anatolia, all four of these metallurgical techniques appears more or less simultaneously at the beginning of the Neolithic c. 7500 BC. However, just as agriculture was independently invented in several parts of the world (including Pakistan, China, and the Americas) copper smelting was invented locally in several different places.

    109. Which of the following is used to remove rust stains on cloth?

    (1) Kerosene 
    (2) Lime
    (3) Oxalic acid solution
    (4) Petrol
    Answer:
    109. (3) Oxalic acid is an organic compound with the formula H2C2O2. It is a colourless crystalline solid that dissolves in water to give colourless solutions. It is classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate . Ingestion of oxalic acid through skin contact or orally is dangerous. Oxalic acid’s main applications include cleaning or bleaching, especially for the removal of rust, e.g. Bar Keepers Friend is an example of a household cleaner containing oxalic acid. About 25% of produced oxalic acid is used as a mordant in dyeing processes. It is used in bleaches, especially for pulpwood. It is also used in baking powder.

    110. Curd is sour due to presence of

    (1) Tartaric acid 
    (2) Lactic acid
    (3) Acetic acid 
    (4) Oxalic acid
    Answer:
    110. (2) Curds are a dairy product obtained by curdling (coagulating) milk with rennet or an edible acidic substance such as lemon juice or vinegar, and then draining off the liquid portion. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. The remaining liquid, which contains only whey proteins, is the whey. In cow’s milk, 80% of the proteins are caseins. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria or yeast) will also naturally produce curds, and sour milk cheese is produced this way. Curd products vary by region and include cottage cheese, quark (both curdled by bacteria and sometimes also rennet) and Indian paneer (milk curdled with lime juice). The word can also refer to a non-dairy substance of similar appearance or consistency, though in these cases a modifier or the word curdled is generally used.

    111. Tear gas is :

    (1) Chloroprene
    (2) Carbonyl chloride
    (3) Nitrous oxide
    (4) Bleaching powder
    Answer:
    111. (2) Tear gas, formally known as a lachrymatory agent or lachrymator (from lacrima meaning “tear” in Latin), is a non-lethal chemical weapon that stimulates the corneal nerves in the eyes to cause tears, pain, and even blindness. Common lachrymators include OC, CS, CR, CN (phenacyl chloride), nonivamide, bromoacetone, xylyl bromide and syn-propanethialS-oxide (from onions). Tear gas works by irritating mucous membranes in the eyes, nose, mouth and lungs, and causes crying, sneezing, coughing, difficulty breathing, pain in the eyes, temporary blindness, etc. Lachrymators are thought to act by attacking sulphydryl functional groups in enzymes. The compound 2-chlorobenzalmalononitrile (also called o-chlorobenzylidenemalononitrile) (chemical formula:C10H5ClN2), a cyanocarbon, is the defining component of a “tear gas” commonly referred to as CS gas, which is used as a riot control agent. CS gas is generally accepted as being non-lethal.

    112. Which of the following compounds is commonly used as an antiseptic in mouthwashes and toothpastes ?

    (1) Borax 
    (2) Saltpetre
    (3) Hydrogen peroxide
    (4) Sodium chloride
    Answer:
    112. (4) Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Antiseptics are generally distinguished from antibiotics by the latter’s ability to be transported through the lymphatic system to destroy bacteria within the body, and from disinfectants, which destroy microorganisms found on non-living objects. Some antiseptics are true germicides, capable of destroying microbes (bacteriocidal), while others are bacteriostatic and only prevent or inhibit their growth. Antibacterials are antiseptics that have the proven ability to act against bacteria. Microbicides which destroy virus particles are called viricides or antivirals. Sodium chloride,Used as a general cleanser. It is also used as an antiseptic mouthwash.

    113. Which one of the following is used to restore the colour of old oilpaintings ?

    (1) Ozone
    (2) Hydrogen peroxide
    (3) Barium peroxide
    (4) Sodium peroxide
    Answer:
    113. (2) Hydrogen peroxide (H2O2) is the simplest peroxide (a compound with an oxygen-oxygen single bond). It is also a strong oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colourless. Due to its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent. The oxidizing capacity of hydrogen peroxide is so strong that it is considered a highly reactive oxygen species. Hydrogen peroxide is therefore used as a propellant in rocketry. Organisms also naturally produce hydrogen peroxide as a byproduct of oxidative metabolism. Consequently, nearly all living things (specifically, all obligate and facultative aerobes) possess enzymes known as catalase peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen.

    114. Milk is a natural

    (1) Solution 
    (2) Emulsion
    (3) Mixture 
    (4) Suspension
    Answer:
    114. (2) An emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable or
    unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both the dispersed and the continuous phase are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, milk, mayonnaise, and some cutting fluids for metal working. The photo-sensitive side of photographic film is also an example of a colloid. The word “emulsion” comes from the Latin word for “to milk”, as milk is (among other things) an emulsion of milk fat and water.

    115. A polymeric substance used to make parachute is

    (1) Rayon 
    (2) Viscose
    (3) Cotton 
    (4) Terylene
    Answer:
    115. (2) Viscose is a viscous organic liquid used to make rayon and cellophane. Viscose is also used as shorthand for Viscose Rayon, thus becoming synonymous with rayon, a soft man-made fibre commonly used in dresses, linings, shirts, shorts, coats, jackets, and other outer wear. It is also used in industrial yarns (tyre cord), upholstery and carpets. Viscose currently is becoming less common because of the polluting effects of carbon disulfide and other by-products of the process, forcing some factories to close. One way to comply with sulphur emission standards is to install a wet sulfuric acid process unit which recovers sulfur compounds to sulfuric acid or use the Lyocell process which uses N-Methylmorpholine N-oxide as solvent.

    116. Drinking soda is

    (1) Alkaline 
    (2) Acidic
    (3) Neutral 
    (4) Oxidant
    Answer:
    116. (2) A soft drink, coke, soda pop, fizzy drink, tonic, seltzer, mineral, sparkling water or carbonated
    beverage) is a beverage that typically contains water (often, but not always carbonated water), usually a
    sweetener, and usually a flavoring agent. The sweetener may be sugar, high-fructose corn syrup,
    fruit juice, sugar substitutes (in the case of diet drinks) or a combination of these. Soft drinks may also contain caffeine, colourings, preservatives and other ingredients. Soft drinks are called “soft” in contrast to “hard drinks” (alcoholic beverages). Small amounts of alcohol may be present in a soft drink, but the alcohol content must be less than 0.5% of the total volume if the drink is to be considered non-alcoholic and is acidic in nature. One hypothesis to explain this relationship is that the phosphoric acid contained in some soft drinks (colas) displaces calcium from the bones, lowering bone density of the skeleton and leading to weakened bones, or osteoporosis.

    117. The cathode of a lead storage battery is made up of

    (1) Zinc 
    (2) Lead
    (3) Lead oxide
    (4) Manganese dioxide
    Answer:
    117. (2) Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of
    rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume
    ratio, their ability to supply high surge currents means that the cells maintain a relatively large power-toweight ratio. These features, along with their low cost, make them attractive for use in motor vehicles to provide the high current required by automobile starter motors. The lead–acid cell can be demonstrated using sheet lead plates for the two electrodes. However such a construction produces only around one ampere for roughly postcard sized plates, and for only a few minutes. The positive plates are the chocolate brown colour of lead dioxide, and the negative are the slate gray of “spongy” lead.

    118. Which one of the following is radioactive ?

    (1) Cesium 
    (2) Platinum
    (3) Strontium 
    (4) Thorium
    Answer:
    118. (4) Thorium is a naturally occurring radioactive chemical element with the symbol Th and atomic
    number 90. It was discovered in 1828 by the Norwegian mineralogist Morten ThraneEsmark and
    identified by the Swedish chemist JonsJakob Berzelius and named after Thor, the Norse god of thunder. In nature, virtually all thorium is found as thorium-232, which undergoes alpha decay with a half-life of about 14.05 billion years. Other isotopes of thorium are short-lived intermediates in the decay chains of higher elements, and only found in trace amounts. Thorium is estimated to be about three to four times more abundant than uranium in the Earth’s crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals. Thorium was once commonly used as the light source in gas mantles and as an alloying material, but these applications have declined due to concerns about its radioactivity.

    119. Heat resistant variety of glass is—

    (1) Pyrex glass 
    (2) Hard glass
    (3) Flint glass 
    (4) None of these
    Answer:
    119. (3) Flint glass is optical glass that has relatively high refractive index and low Abbe number (high
    dispersion). Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The
    currently known flint glasses have refractive indices ranging between 1.45 and 2.00. A concave lens of
    flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet lens because of their compensating optical properties, which reduces chromatic aberration (colour defects). Flint glass also bear the property of heat resistant. Traditionally, flint glasses were lead glasses containing around 4–60% lead oxide; however, the manufacture and disposal of these glasses were sources of pollution. In many modern flint glasses, the lead can be replaced with other additives such as titanium dioxide and zirconium dioxide without significantly altering the optical properties of the glass. Electric Bulbs and Spectacle glasses are made of Flint glass.

    120. Among the following iron ores, the highest percentage of iron content is found in—

    (1) Haemetite 
    (2) Magnetite
    (3) Limnonite 
    (4) None of these
    Answer:
    120. (1) Hematite, also spelled haematite, heavy and relatively hard oxide mineral, ferric oxide (Fe2O3), that constitutes the most important iron ore because of its high iron content (70 percent) and its abundance. Its name is derived from the Greek word for “blood,” in allusion to its red colour. Many of the various forms of hematite have separate names. The steel-gray crystals and coarse-grained varieties have a brilliant metallic lustre and are known as specular iron ore; thin scaly types are called micaceous hematite. Much hematite occurs in a soft, fine-grained, earthy form called red ochre or ruddle. Intermediate between these types are compact varieties, often with a reniform surface (kidney ore) or a fibrous structure (pencil ore). Red ochre is used as a paint pigment; a purified form, rouge, is used to polish plate glass. The most important deposits of hematite are sedimentary in origin. The world’s largest production (nearly 75 million tons of hematite annually) comes from a sedimentary
    deposit in the Lake Superior district in North America.


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