General Science Mixed Quiz: Set 30

The correct answer is A, aluminium oxide. An amphoteric oxide reacts with both acids and bases to give a salt and water. Aluminium oxide dissolves in hydrochloric acid to give aluminium chloride and in sodium hydroxide to give sodium aluminate, so it behaves as a base in one case and as an acid in the other. Zinc oxide behaves the same way. Option B is wrong because iron oxide is a basic oxide, reacting with acids but not with alkalis. Option C is wrong because magnesium oxide is strongly basic; dissolved in water it gives an alkaline solution and it reacts only with acids. Option D is wrong because carbon dioxide is a typical acidic oxide of a non-metal, giving carbonic acid with water and reacting with bases such as lime water. The two amphoteric oxides most often asked for are those of aluminium and zinc.

The correct answer is B, Cones. Cones are the photoreceptor cells of the retina that respond to colour in bright light. The human retina carries two kinds of photoreceptors. Cones number about six to seven million, sit densely near the centre of the retina and come in three types, sensitive to red, green and blue light; the brain mixes their signals into every shade we see. They work only when the light is good, which is why colours fade at dusk. Option A is wrong because rods are far more numerous but work in dim light and give only shades of grey, not colour. Option C is wrong because the blind spot is the point where the optic nerve leaves the eyeball and carries no photoreceptors at all. Option D is wrong because the fovea is a small pit in the retina, a place rather than a cell type, although it is packed with cones. Exam tip: rods for night and grey, cones for colour and daylight; colour blindness is a defect of the cones.

The correct answer is B, NaHCO3. Baking soda is sodium hydrogen carbonate, a mild, non corrosive base used as an antacid, as an ingredient of baking powder along with a mild edible acid such as tartaric acid, and in soda acid fire extinguishers, where it releases carbon dioxide. Option A is wrong because Na2CO3 is sodium carbonate, and its decahydrate is washing soda, used for cleaning and for softening hard water. Option C is wrong because NaOH is sodium hydroxide, caustic soda, a strong alkali obtained from the chlor alkali process. Option D is wrong because CaOCl2 is bleaching powder, made by passing chlorine over dry slaked lime. The pair that catches students out is sodium carbonate against sodium hydrogen carbonate, so remember that the one with hydrogen in the name is the baking soda used in the kitchen.

The correct answer is C, a mechanism to reduce CO2 emission. A nuclear reactor splits heavy atoms; it burns no fuel, so it releases no carbon dioxide and needs no equipment to cut such emissions. The heat of fission is produced in the reactor core, carried away by a coolant, passed to water in a heat exchanger or steam generator, and the steam then turns a turbine coupled to a generator. Control rods of cadmium or boron absorb spare neutrons and a moderator such as heavy water slows them down so that fission continues steadily. Option A is wrong as a choice because the turbine is the part that actually converts steam energy into electricity. Option B is wrong because the heat exchanger carries heat from the radioactive coolant loop to the clean water loop. Option D is wrong because the reaction chamber, the core holding the fuel rods, is where fission happens. Exam tip: a nuclear plant emits no carbon dioxide; its waste problem is spent radioactive fuel instead.

The correct answer is D, Areolar. Animal tissues are grouped into four kinds — epithelial, muscular, connective and nervous — and areolar is not one of them, because it is only a type of connective tissue. Areolar tissue is the loose packing tissue found between the skin and the muscles, around blood vessels and nerves and inside bone marrow, where it fills space, supports organs and helps repair damaged parts. Since it sits inside the connective group, putting it beside the four main classes is exactly the mistake the question wants you to catch. Option A is wrong because epithelial tissue is one of the four and covers and lines all body surfaces and cavities. Option B is wrong because muscular tissue, made of contractile fibres of three sorts — striated, smooth and cardiac — is also one of the four. Option C is wrong because connective tissue is a main class and takes in bone, cartilage, blood, tendon, ligament, adipose and areolar tissue itself. Exam tip: four animal tissues — epithelial, muscular, connective, nervous; blood, bone and areolar are all connective.

The correct answer is A, Used on ordinary combustibles such as wood and paper. Fires are sorted into classes by what is burning, and Class A covers ordinary solid fuels — wood, paper, cloth, straw, rubber and many plastics. These fires leave glowing embers, so they are put out mainly by cooling, and plain water or a water-based extinguisher is the cheapest and most effective choice for them. Option B is wrong because burning liquids such as petrol, kerosene, oil, paint and solvents are Class B, where water would spread the fire and foam or dry powder is used instead. Option C is wrong because a fire in live electrical equipment is a separate class — Class C in the American scheme and marked Class E in the Indian and European ones — and it needs a non-conducting agent such as carbon dioxide, never water. Option D is wrong because burning metals such as magnesium, sodium and potassium form Class D and need a special dry powder, since water reacts violently with them. Exam tip: A — solids, B — liquids, C — gases, D — metals, F or K — cooking oil.

The correct answer is D, Black. In the colour code used for fire extinguishers, a black band or label marks a carbon dioxide extinguisher. The body of the cylinder is signal red and a coloured patch near the label tells you the filling at a glance, so the right cylinder can be picked in a hurry. A carbon dioxide extinguisher works by smothering: the gas is heavier than air, so it pushes oxygen away from the fuel, and it also chills the surface as it expands out of the horn. Because it does not conduct electricity and leaves no residue, it is the choice for live electrical equipment, switchboards, laboratories and computer rooms. Option A is wrong because a red band marks a plain water extinguisher, used on wood and paper fires. Option B is wrong because blue marks dry powder, the all-purpose filling for liquid and gas fires. Option C is wrong because cream, not white, is the colour for a foam extinguisher. Exam tip: red — water, cream — foam, blue — dry powder, black — carbon dioxide, yellow — wet chemical.

The correct answer is D, Ligament. A ligament is the connective tissue that joins one bone to another at a joint. It is very elastic and strong, and it holds the bones in place so that a joint can move without the bones slipping apart. Ligaments contain little matrix of their own and are stretched when a joint is twisted, which is what happens in a sprain. A is wrong because a tendon joins a muscle to a bone; tendons are fibrous and strong but have limited stretch, so the pull of a muscle is passed straight to the bone. B is wrong because cartilage is the smooth, flexible tissue that pads the ends of bones and shapes the nose and ear, cushioning the joint rather than tying the bones together. C is wrong because matrix is the material in which the cells of a connective tissue are embedded, not a structure by itself. Exam tip: ligament bone to bone, tendon muscle to bone.

The correct answer is B, Hydra. Hydra is the one animal in the list that reproduces both by budding and by regeneration.

In budding, a bulge grows out from the body wall of the parent Hydra, develops a mouth and tentacles, and then breaks off as a small independent Hydra. In regeneration, a piece cut from the body grows the missing parts back and becomes a complete animal, because Hydra keeps a large store of unspecialised cells that can turn into any tissue. Both are forms of asexual reproduction, so the young are copies of the parent.

Option A is wrong because Planaria is the classic example of regeneration alone and does not bud. Option C is wrong because Amoeba divides into two by binary fission. Option D is wrong because yeast reproduces only by budding, and it is a fungus, not an animal.

Exam tip: Hydra shows budding and regeneration, Planaria only regeneration, Amoeba binary fission, Plasmodium multiple fission.

The correct answer is B, tuberculosis (TB). The BCG vaccine takes its name from Albert Calmette and Camille Guerin, the two French scientists who developed it from a weakened strain of Mycobacterium bovis. In India it is given as a single dose soon after birth under the Universal Immunisation Programme, and it protects infants mainly from the severe forms of the disease, such as tuberculous meningitis and miliary tuberculosis. Tuberculosis itself is caused by the bacterium Mycobacterium tuberculosis, identified by Robert Koch in 1882, and it spreads through droplets when a patient coughs. Option A is wrong because typhoid, caused by Salmonella typhi, has its own conjugate vaccine. Option C is wrong because mumps is a viral disease covered by the MMR vaccine along with measles and rubella. Option D is wrong because plague, caused by Yersinia pestis and carried by rat fleas, needs a different vaccine. Exam tip: BCG at birth for TB, and World TB Day falls on 24 March.

The correct answer is B, Fallopian tube. In human beings the sperm meets and fuses with the egg inside the fallopian tube, also called the oviduct.

The ovary releases one egg in a month, and the funnel shaped mouth of the fallopian tube collects it. Sperms swim up from the vagina through the cervix and the uterus into the tube, and fusion usually happens in its wider upper part. The fertilised egg, now a zygote, begins to divide as the tube's lining pushes it along, and reaches the uterus in a few days as a ball of cells that implants in the thick uterine wall and grows there with the help of the placenta.

Option A is wrong because the uterus is where the embryo implants and develops, after fertilisation. Option C is wrong because the ovary only makes and releases the egg. Option D is wrong because the vagina is the passage the sperms enter through.

Exam tip: egg made in the ovary, fertilised in the fallopian tube, developed in the uterus.

The correct answer is A, Distillation. Distillation separates a liquid from a solution or from another liquid by boiling it and condensing the vapour, so it is used when the components differ in boiling point, as in getting pure water from salt water or separating acetone from water. It is not the method for purifying a solid mixed with solid impurities. Option B is useful because sublimation purifies a solid that turns straight into vapour on heating, such as camphor, naphthalene, iodine or ammonium chloride, leaving the non-volatile impurity behind. Option C is useful because crystallization dissolves the solid in a hot solvent and lets pure crystals form on cooling, the standard way to purify alum, copper sulphate and sugar. Option D is wrong because two of the three processes do purify solids, so they cannot all be useless. Exam tip: solids are purified by sublimation, crystallization and chromatography; distillation is for liquids.

The correct answer is C, Hepatitis B. The hepatitis B vaccine was the first vaccine made by recombinant DNA technology. Scientists cut out the gene for the surface protein of the hepatitis B virus and put it into yeast cells; the yeast then made that protein in large amounts, and the purified protein is injected as the vaccine. Because only one viral protein is used and no whole virus is involved, the vaccine cannot cause the disease, which is what makes recombinant vaccines safe. It was licensed in the mid 1980s and in India it is part of the pentavalent shot given to infants. A is wrong because the polio vaccine is either the killed virus of Salk or the weakened live virus of Sabin. B is wrong because no vaccine against AIDS has been licensed so far. D is wrong because the smallpox vaccine used the live vaccinia virus, and the disease was declared eradicated in 1980. Exam tip: hepatitis B, first recombinant vaccine, made in yeast from the surface antigen gene.

The correct answer is D, Above the center of gravity. When a floating body tilts a little, the centre of buoyancy shifts to the centre of the newly displaced water, and the vertical drawn through it cuts the original axis of the body at a point called the metacentre. If that point lies above the centre of gravity, the weight and the upthrust form a couple that turns the body back to its old position, so the equilibrium is stable; the gap between the two points is the metacentric height, and a larger value gives a stiffer, quicker roll. Option A is the opposite case: with the metacentre below the centre of gravity the same couple tips the body further over, which is unstable equilibrium, and if the two coincide the body is in neutral equilibrium. Options B and C are wrong because the metacentre's position relative to the centre of buoyancy decides nothing; only its position relative to the centre of gravity does. Exam tip: M above G is stable, M below G capsizes.

The correct answer is A, Ashwagandha. Ashwagandha, whose botanical name is Withania somnifera, is called winter cherry in English because of the small red berry it bears inside a papery cover; it is also called Indian ginseng. The part used is the root, which in Ayurveda is given as a tonic for weakness, stress and sleeplessness, and the plant's Sanskrit name comes from the horse-like smell of the fresh root. It is a hardy shrub of dry regions, so Rajasthan, Madhya Pradesh and Gujarat are the main growing states; the Nagauri type from Nagaur in Rajasthan and the crop around Mandsaur and Neemuch in Madhya Pradesh are the best known. B is wrong because rose is an ornamental and perfume crop, not a winter cherry. C is wrong because lily is a garden flower grown from bulbs. D is wrong because chandni is an ornamental flowering shrub grown for its white flowers. Exam tip: Ashwagandha, Withania somnifera, winter cherry or Indian ginseng, root used.

The correct answer is D, Tunnel diode. A tunnel diode, also called an Esaki diode after Leo Esaki who made it in 1957, is heavily doped on both sides, so its depletion layer is extremely thin and electrons cross it by quantum tunnelling. Over part of its forward characteristic the current falls as the voltage rises, giving a negative resistance region, and it is this property that lets the diode both amplify a signal and sustain oscillations in a circuit. It switches extremely fast and is used in microwave oscillators and high frequency circuits. A is wrong because a point contact diode is used to detect and rectify high frequency signals. B is wrong because a Zener diode works in reverse breakdown and is used to regulate voltage. C is wrong because an ordinary junction diode only rectifies, allowing current one way. Exam tip: tunnel diode means negative resistance, so it can amplify and oscillate; Zener diode means voltage regulation.

The correct answer is A, Capra aegagrus hircus. The domestic goat is treated as a subspecies of the wild goat, so its name carries three parts — the genus Capra, the species aegagrus and the subspecies hircus. It is often shortened to Capra hircus. Carl Linnaeus gave science this binomial system, in which the genus name begins with a capital letter, the species name does not, and the whole name is printed in italics or underlined when handwritten. Goats were among the first animals humans tamed, in western Asia roughly ten thousand years ago, and India keeps one of the largest goat populations in the world. Option B is wrong because Bos indicus is the humped Indian cattle, the zebu. Option C is wrong because Sus scrofa is the wild boar, the ancestor of the domestic pig. Option D is wrong because Ovis aries is the domestic sheep, the animal most often confused with the goat in such questions. Exam tip: goat Capra hircus, sheep Ovis aries, cattle Bos indicus, buffalo Bubalus bubalis.

The correct answer is A, Crown Gall. Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there. The bacterium works by pushing a piece of its own Ti plasmid into the plant's cells and forcing them to divide, and that natural trick is why laboratories use it as a vector to carry new genes into plants. Grapevine, apple, rose, walnut and stone fruits suffer the most. Option B is wrong because mosaic diseases, such as tobacco mosaic, are caused by viruses that mottle the leaves in light and dark patches. Option C is wrong because smut of wheat, bajra and sugarcane is a fungal disease that fills the ear with black powdery spores. Option D is wrong because white blister, or white rust, of crucifers such as mustard is also fungal and raises white blisters on leaves and stems. Exam tip: bacterial — crown gall, citrus canker, bacterial blight of rice; viral — mosaic, leaf curl; fungal — smut, rust, blight.

The correct answer is B, Ni, that is, nickel. Vegetable oils contain unsaturated fatty acids with carbon-carbon double bonds, and when hydrogen is passed through the oil at about 60 degrees Celsius in the presence of finely divided nickel, the double bonds add hydrogen and become saturated, turning the liquid oil into semi-solid vanaspati. Option A is wrong because lead is not a hydrogenation catalyst; it is in fact used as a catalyst poison in some reactions. Option C is wrong because hydrogen is the reactant being added across the double bond, not the catalyst, and the question asks for the substance that speeds the reaction without being consumed. Option D is wrong because helium is a noble gas, chemically inert, and takes no part in any such reaction. Remember the set of industrial catalysts: nickel for hydrogenation, iron for the Haber process and vanadium pentoxide for the contact process.

The correct answer is A, formic acid. The sting of an ant and the hairs of the nettle plant inject formic acid, also called methanoic acid, which is why the skin burns; rubbing on a mild base such as baking soda or the leaf of the dock plant relieves it by neutralising the acid. Option B is wrong because citric acid belongs to lemon, orange and other citrus fruits. Option C is wrong because lactic acid is formed in curd and sour milk, and also in muscles during heavy exercise. Option D is wrong because tartaric acid is found in tamarind and grapes and is used with baking soda in baking powder. This question is a favourite because it also carries a neutralisation idea with it: the treatment for an acidic ant sting is a base, while a wasp sting, which is alkaline, is treated with a mild acid such as vinegar.