Chemistry GK Questions Quiz-7

Chemistry GK Questions Quiz-7

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

    121. Pasteurisation of milk means–

    (1) heating of milk to above 72°C
    (2) heating of milk to above 62°C
    (3) cooling of milk to about 62°C
    (4) cooling of milk to about 10°C
    Answer:
    121. (2) Pasteurization typically uses temperatures below boiling, since at very high temperatures, casein micelles will irreversibly aggregate, or “curdle”. The two main types of pasteurization used today are: hightemperature, short-time (HTST) and “extended shelf life” (ESL) treatment. Ultra-high temperature (UHT or ultra-heat-treated) is also used for milk treatment. In the HTST process, milk is forced between metal plates or through pipes heated on the outside by hot water, and is heated to 71.7degree C (161degree F) for 15– 20 seconds. UHT processing holds the milk at a temperature of 135degree C (275degree F) for a minimum of one second. ESL milk has a microbial filtration step and lower temperatures than UHT milk. Milk simply labeled “pasteurized” is usually treated with the HTST method, whereas milk labeled “ultrapasteurized” or simply “UHT” has been treated with the UHT method. A less conventional but US FDAlegal alternative (typically for home pasteurization) is to heat milk at 145 degree F (63 degree C) for 30 minutes.

    122. Aluminium can be purified by

    (1) oxidation 
    (2) distillation
    (3) electrolysis 
    (4) ozonolysis
    Answer:
    122. (3) Electrolysis is a method of using a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. Aluminum is extracted from its oxide ore “Bauxite”. Electrolytic smelting of alumina was originally cost-prohibitive in part because of the high melting point of alumina, or aluminium oxide. Many minerals, however, will dissolve into a second already molten mineral, even if the temperature of the melt is significantly lower than the melting point of the first mineral. Molten cryolite was discovered to
    dissolve alumina at temperatures significantly lower than the melting point of pure alumina without
    interfering in the smelting process.

    123. Impure camphor is purified by

    (1) sublimation
    (2) fractional crystallisation
    (3) fractional distillation
    (4) steam distillation
    Answer:
    123. (1) Sublimation apparatus is a piece of laboratory glassware used in the technique of sublimation usually used by chemists to purify compounds. Typically a solid is placed in a vessel which is then heated under vacuum. Under this reduced pressure the solid volatilizes and condenses as a purified compound on a cooled surface, leaving the non-volatile residue impurities behind. This cooled surface often takes the form of a cold finger. Once heating ceases and the vacuum is released, the sublimed compound can be collected from the cooled surface. Impure camphor is purified by this process.

    124. Greenhouse effect is caused by

    (1) nitrogen
    (2) carbon dioxide
    (3) carbon monoxide
    (4) nitrogen dioxide
    Answer:
    124. (2) The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases. By their percentage contribution to the greenhouse effect on Earth the four major gases are: water vapor, 36–70%, carbon dioxide, 9– 26%,methane, 4–9% and ozone, 3–7%.

    125. Type metal used in printing press is an alloy of

    (1) lead and copper
    (2) lead and antimony
    (3) lead and bismuth
    (4) lead and zinc
    Answer:
    125. (2) In printing, type metal (sometimes called hot metal) refers to the metal alloys used in traditional typefounding and hot metal typesetting. Lead is the main constituent of these alloys. Antimony and tin are added to make the character produced durable and tough while reducing the difference between the coefficients of expansion of the matrix and the alloy. Cheap, plentifully available as galena and easily workable, lead has many of the ideal characteristics, but on its own it lacks the necessary hardness and does not make castings with sharp details because molten lead shrinks and sags when it cools to a solid.

    126. Sour taste of ‘Coca Cola’ is due to the presence of

    (1) acetic acid
    (2) phosphoric acid
    (3) hydrochloric acid
    (4) formic acid
    Answer:
    126. (2) Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas, but not without controversy regarding its health effects. It provides a tangy or sour taste and, being a mass-produced chemical, is available cheaply and in large quantities. The low cost and bulk availability is unlike more expensive seasonings that give comparable flavors, such as citric acid which is obtainable from citrus, but usually fermented by Aspergillusniger mold from scrap molasses, waste starch hydrolysates and phosphoric acid.

    127. Bhopal gas tragedy is associated with leakage of

    (1) carbon dioxide
    (2) nitrogen dioxide
    (3) sulphur dioxide
    (4) methyl isocyanate
    Answer:
    127. (4) The Bhopal disaster, also referred to as the Bhopal gas tragedy, was a gas leak incident in India,
    considered one of the world’s worst industrial disasters. It occurred on the night of 2–3 December,
    1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh. Over
    500,000 people were exposed to methyl isocyanate gas and other chemicals. The toxic substance made
    its way in and around the shantytowns located near the plant. Estimates vary on the death toll. The official immediate death toll was 2,259. The government of Madhya Pradesh confirmed a total of 3,787 deaths related to the gas release. Others estimate 8,000 died within two weeks and another 8,000 or more have since died from gas-related diseases.

    128. Iodized salt is beneficial for

    (1) lowering of blood pressure
    (2) prevention of dehydration
    (3) thyroid function
    (4) salivary glands
    Answer:
    128. (3) Iodized salt (also spelled iodised salt) is table salt mixed with a minute amount of various salts of the element iodine. The ingestion of iodide prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of mental retardation. Deficiency also causes thyroid gland problems, including “endemic goitre.” In many countries iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the sodium chloride salt.

    129. The acid rain destroys vegetations because it contains

    (1) nitric acid
    (2) ozone
    (3) carbon monoxide
    (4) sulphuric acid
    Answer:
    129. (4) Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxides, which react with the water molecules in the atmosphere to produce acids. Governments have made efforts since the 1970s to reduce the release of sulfur dioxide into the atmosphere with positive results. Nitrogen oxides can also be produced naturally by lightning strikes and sulfur dioxide is produced by volcanic eruptions. The chemicals in acid rain can cause paint to peel, corrosion of steel structures such as bridges, and erosion of stone statues.

    130. Diamonds are glittering and attractive because light incident on them undergoes

    (1) highest refraction
    (2) multiple internal reflections
    (3) multiple surface reflections
    (4) hundred percent transmission
    Answer:
    130. (2) Diamond has remarkable optical characteristics. Because of its extremely rigid lattice, it can be
    contaminated by very few types of impurities, such as boron and nitrogen. Combined with wide
    transparency, this results in the clear, colourless appearance of most natural diamonds. Small amounts
    of defects or impurities (about one per million of lattice atoms) colour diamond blue (boron), yellow (nitrogen), brown (lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion (ability to disperse light of different colours), which results in its characteristic luster. Excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gemstone.

    131. The substance most commonly used as a food preservative is

    (1) sodium carbonate
    (2) tartaric acid
    (3) acetic acid
    (4) sodium salt of benzoic acid
    Answer:
    131. (4) A preservative is a naturally occurring or synthetically produced substance that is added to
    products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent
    decomposition by microbial growth or by undesirable chemical changes. Preservative food additives can be used alone or in conjunction with other methods of food preservation. Preservatives may be antimicrobial preservatives, which inhibit the growth of bacteria or fungi, including mold or they can be antioxidants such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include sorbic acid and its salts, benzoic acid and its salts, calcium propionate, sodium nitrite (and sodium nitrate which converts to sodium nitrite “in situ”), sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.) and disodium EDTA.

    132. Catalyst is a substance which

    (1) increases the rate of the reaction
    (2) decreases the rate of reaction
    (3) has no action on the rate of the reaction
    (4) None of these
    Answer:
    132. (4) Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations. Catalysts that speed the reaction are called positive catalysts. Substances that slow a catalyst’s effect in a chemical reaction are called inhibitors. Substances that increase the activity of catalysts are called promoters, and substances that deactivate catalysts are called catalytic poisons.

    133. Which of the following gases is most toxic ?

    (1) Carbon dioxide
    (2) Carbon monoxide
    (3) Sulphur dioxide
    (4) Chlorine
    Answer:
    133. (2) Carbon monoxide (CO) is a colourless, odorless, and tasteless gas that is slightly lighter than air. It is toxic to humans and animals when encountered in higher concentrations, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions. In the atmosphere it is spatially variable, short lived, having a role in the formation of ground-level ozone. Carbon monoxide is colourless, odorless, and tasteless, but highly toxic. It combines with hemoglobin to produce carboxyhemoglobin, which is ineffective for delivering oxygen to bodily tissues. Concentrations as low as 667 ppm may cause up to 50% of the body’s hemoglobin to convert to carboxyhemoglobin. A level of 50% carboxyhemoglobin may result in seizure, coma, and fatality.

    134. Sour milk contains

    (1) acetic acid 
    (2) tartaric acid
    (3) citric acid 
    (4) lactic acid
    Answer:
    134. (4) Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3. Lactic acid is found primarily in sour milk products, such as koumiss, laban, yogurt, kefir, and some cottage cheeses. The casein in fermented milk is coagulated (curdled) by lactic acid. Lactic acid is also responsible for the sour flavor of sour dough breads. This acid is used in beer brewing to lower the wort pH in order to reduce some undesirable substances such as tannins without giving off-flavors such as citric acid and increase the body of the beer.

    135. The acid used in lead storage cells is

    (1) phosphoric acid
    (2) hydrochloric acid
    (3) nitric acid
    (4) sulphuric acid
    Answer:
    135. (4) 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. In the discharged state both the
    positive and negative plates become lead (II) sulfate (PbSO4) and the electrolyte loses much of its
    dissolved sulfuric acid and becomes primarily water. The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit.

    136. Alum stops bleeding in minor cuts because of

    (1) solvation 
    (2) emulsion
    (3) dialysis 
    (4) coagulation
    Answer:
    136. (4) Coagulation is the process by which blood forms clots. It is an important part of homeostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Disorders of coagulation can lead to an increased risk of bleeding (hemorrhage) or obstructive clotting (thrombosis). Alum in block form (usually potassium alum) is used as a blood coagulant. Styptic pencils containing aluminium sulfate or potassium aluminium sulfate are used as astringents to prevent bleeding from small shaving cuts. For example, alum blocks are commonly sold in pharmacies in India.

    137. ‘Plaster of Paris’ is made by partial dehydration of

    (1) epsom salt(
    (2) gypsum salt
    (3) blue vitriol 
    (4) green vitriol
    Answer:
    137. (2) Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting, and can be easily manipulated with metal tools or even sandpaper. These characteristics make plaster suitable for a finishing, rather than a load-bearing material. The term plaster can refer to gypsum plaster (also known as plaster of Paris), lime plaster, or cement plaster. Plaster of Paris can be used to impregnate gauze bandages to make a sculpting material called modroc. It is used similarly to clay, as it is easily shaped when wet, yet sets into a resilient and lightweight structure.

    138. Water can be separated from alcohol water mixture by

    (1) decantation 
    (2) evaporation
    (3) distillation 
    (4) sublimation
    Answer:
    138. (3) Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process,  and not a chemicalreaction. Commercially, distillation has a number of applications. It is used to separate crude oil into more fractions for specific uses such as transport, power generation and heating. Water is distilled to remove impurities, such as salt from seawater. Air is distilled to separate its components—notably oxygen, nitrogen, and argon— for industrial use. Distillation of fermented solutions has been used since ancient times to produce distilled beverages with a higher alcohol content. The premises where distillation is carried out, especially distillation of alcohol, are known as a distillery.

    139. ‘Milk Sugar’ is

    (1) Lactose 
    (2) Maltose
    (3) Galactose 
    (4) Sucrose
    Answer:
    139. (1) Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk (by weight), although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from lac or lactis, the Latin word for milk, plus the -ose ending used to name sugars. It has a formula of C12H22O11. Food industry applications, both of pure lactose and lactosecontaining dairy by-products, have markedly increased since the 1960s. For example, its bland flavor has lent to its use as a carrier and stabiliser of aromas and pharmaceutical products. Lactose is not added directly to many foods, because it is not sweet and its solubility is less than other sugars commonly used in food. Infant formula is a notable exception where the addition of lactose is necessary to match the composition of human milk.

    140. Petroleum is a mixture of

    (1) elements 
    (2)hydrocarbons
    (3) polymers 
    (4) salts
    Answer:
    140. (2) Petroleum or crude oil is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth’s surface. A fossil fuel, it is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure. Petroleum is recovered mostly through oil drilling. This comes after the studies of structural geology (at the reservoir scale), sedimentary basin analysis, reservoir characterization (mainly in terms of porosity and permeable structures)


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