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Part 065 – Chemistry Previous Year Questions

Q1. The term ‘brown air’ is used for
(a) Acid fumes
(b) Photochemical smog
(c) Sulphurous smog
(d) Industrial smog
Ans: (b) Photochemical smog which is mainly composed of ozone (O3), Peroxyacetyl nitrate (PAN) and Nox, is also known as brown air where solar radiation is intense. In seasons of lesser solar radiation or areas, smog formation is incomplete and the air is referred to as grey air.

Q2. What happens when a drop of glycerol is added to crushed KMnO4 spread on a paper ?

(a) There is a crackling sound.
(b) There is a violent explosion.
(c) There is no reaction.
(d) The paper ignites.

Ans: (b) When solid Potassium Permanganate (KMnO4) is mixed with pure glycerol or other simple alcohols, it will result in a violent combustion reaction. Potassium Permanganate is an extremely powerful oxidizer which spontaneously ignites after coming in contact with glycerol. The glycerol is oxidized so quickly that heat is generated faster than it can be dissipated. 3 C3H5(OH)3 + 14 KMnO4 14 MnO2 + 7 K2CO3 + 2 CO2 + 12 H2O

Q3. Most commonly used bleaching agent is

(a) Sodium chloride
(b) Alcohol
(c) Carbon dioxide
(d) Chlorine
Ans: (d) Chlorine is used to disinfect water and is part of the sanitation process for sewage and industrial waste. During the production of paper and cloth, it is used as a bleaching agent. It is also used in cleaning products; including household bleach which is chlorine dissolved in water Bleaching powder is an important and a commonly used bleaching agent prepared from chlorine.

Q4. Which of the following can be found as pollutants in the drinking water in some parts of India?
Select the correct answer using the code given below.
(A) Arsenic
(B) Sorbitol
(C) Fluoride
(D) Formaldehyde
(E) Uranium

(a) B, D and E
(b) A, B, C, D and E
(c) A, C and E
(d) A and C
Ans: (c) Recent research has shown that India’s groundwater faces the problem of presence of uranium, arsenic, and heavy metals in ground water used for drinking. Sorbitol (used as artificial sweetener) and Formaldehyde (used in coating, etc) are not famous as water pollutants.

Q5. Cyanide poisoning causes death in seconds because

(a) It denatures enzymes of the heart/muscle
(b) It breaks the electron transport chain
(c) It causes Lysis of red blood cells.
(d) It causes cardiac arrest
Ans: (d) Cyanide poisoning occurs on exposure to a compound that produces cyanide ions when dissolved in water. The cyanide ion halts cellular respiration by inhibiting an enzyme in the mitochondria called cytochrome c oxidase. If cyanide is inhaled it causes a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds.

Q6. The ore of Aluminium is

(a) Fluorspar (b) Bauxite
(c) Chalco pyrites (d) Hematite
Ans: (b) Bauxite, an aluminium ore, is the world’s main source of aluminium. Bauxite is primarily comprised of aluminum oxide compounds (alumina), silica, iron oxides and titanium dioxide. It is refined through the Bayer chemical process into alumina. Alumina is refined into pure aluminum metal through the Hall– Héroult electrolytic process.

Q7. Heavy metals got their name because compared to other atoms they have

(a) Higher densities
(b) Higher atomic masses
(c) Higher atomic numbers
(d) Higher atomic radii
Ans: (b) Arsenic, beryllium, cadmium, chromium, lead, manganese, mercury, nickel, and selenium are some of the metals called ‘heavy’ because of their high relative atomic mass. They persist in nature and can cause damage or death in animals, humans, and plants even at very low concentrations.

Q8. Photo chemical smog is a resultant of the reaction among

(a) High concentration of NO2, O3, and CO in the evening
(b) CO, CO2 and NO2 at low temperature.
(c) CO, O2 and peroxy acetyl nitrate in the presence of Sunlight
(d) NO2, O3 and peroxy acetyl nitrate in the presence of Sunlight
Ans: (d) Photochemical smog is a unique type of air pollution which is caused by reactions between sunlight and pollutants like hydrocarbons and nitrogen dioxide (NO and NO2). Other components of the photochemical smog include Ozone (O3) formaldehyde, peroxy benzoyl nitrate (PBzN), peroxy acetyl nitrate (PAN) and acrolein. The formation of photochemical smog can be expressed in the simple terms as: Hydrocarbons + NOx + sunlight

Q9. Which of the following particles has the dual nature of particle– wave?

(a) Electron (b) Meson
(c) Proton (d) Neutron
Ans: (a) n 1905, it was Einstein who suggested the concept of light having a dual nature; particle and wave nature. In a similar way, Louise de Broglie suggested that electron also exhibits a dual nature. Broglie derived a mathematical expression to prove the wave nature of electron along with particle nature. He gave the following relation:- ë =h/mí, where ë is the wavelength of electron, m is mass of an electron and í is the frequency.

Q10. Ultra purification of a metal is done by :

(a) slugging (b) zone melting
(c) smelting (d) leaching
Ans: (b) When metals are required in a ultra pure state, the zone refining method is used. The principle-employed states that the impurities, which lower the melting point of a metal remain preferentially dissolved in the liquid phase and purer metal will emerge in the solid phase.

Q11. The soft silvery metalic element which ionizes easily when heated or exposed to light and is present in atomic clocks is :

(a) Cerium (b) Cesium
(c) Calcium (d) Califonrium
Ans: (b) In 1967, based on Einstein defining the speed of light as the most constant dimension in the universe, the International System of Units isolated two specific wave counts from an emission spectrum of caesium- 133 to co-define the second and the meter. Since then, caesium has been widely used in highly accurate atomic clocks. Among alkali metals, cesium has lowest ionization energy and hence it can show photoelectric effect to the maximum extent.

Q12. Catalytic converters are generally made from :

(a) Alkaline metals
(b) Hydrogen
(c) Transition metals
(d) Carbon
Ans: (c) Transition metals are used directly as catalysts in the anti–pollution catalytic converters in car exhausts. For example, expensive transition metals such as Platinum and rhodium are used in the catalytic converters in car exhausts to reduce the emission of carbon monoxide and nitrogen monoxide, which are converted to the non–polluting gases nitrogen and carbon dioxide. 2NO (g) + 2CO(g) N2 (g) + 2CO2 (g)

Q13. The green colour seen in firework displays is due to the chloride salt of :

(a) Sodium (b) Strontium
(c) Barium (d) Calcium
Ans: (c) The red, orange, yellow, green, blue and purple colors exploding in the night sky during a pyrotechnic festival are created by the use of metal salts. Barium chloride provides green colour to firework displays. Metal salts that are commonly used in firework displays include: strontium carbonate (red), calcium chloride (orange), sodium nitrate (yellow), barium chloride (green fireworks) and copper chloride (blue fireworks).

Q14. The radiation that can penetrate deepest in our body

(a) UV-radiation
(b) Alpha-particles
(c) -particles
(d) Gamma-particles
Ans: (d) The ability of radioactivity to pass through materials is called its penetrating ability. Penetrating ability depends on the size of the radioactive particle. Alpha particles are the biggest, beta particles are very much smaller and gamma rays have no mass. Ultraviolet rays have less energetic photons compared to gamma rays and x-rays and a lower penetration power. Gamma rays are the most penetrating of the radiations.

Q15. Which one of the following does not contain silver ?

(a) Horn silver
(b) Ruby silver
(c) German silver
(d) Lunar caustic
Ans: (c) German Silver (also known as New Silver, Nickel Brass, etc) is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. It is named for its silvery appearance, but it contains no elemental silver unless plated.

Q16. An important green-house gas other than methane being produced from the agricultural fields is

(a) Nitrous oxide
(b) Ammonia
(c) Sulphur dioxide
(d) Arsine
Ans: (a) Nitrous oxide (N2O) and methane (CH4) are the two major greenhouse gasses (GHG) emitted by agricultural activities. N2O accounts for around 8% of the warming impact of current human GHG emissions. Agricultural activities that directly increase N2O emissions are: fertilization, application of manure or other organic materials, retention of crop residues, production of nitrogen-fixing crops and forages, and cultivation of soils with high organic matter content. Irrigation, drainage, tillage practices and fallowing of land also increase N2O emission.

Q17. Acid rain is caused due to pollution of atmosphere by

(a) oxides of carbon and nitrogen
(b) oxides of nitrogen and sulphur
(c) oxides of nitrogen and phosphorus
(d) None of these
Ans: (b) Acid rain is caused by emissions of Sulfur Dioxide (SO2) and Nitrogen Oxide (NOx), which react with the water molecules in the atmosphere to produce acids. Emissions of SO2 and NOx result from fossil fuel combustion. The chemicals in acid rain can cause paint to peel, corrosion of steel structures such as bridges, and erosion of stone statues.

Q18. Which of the following chemicals is responsible for depletion of ozone layer in the atmosphere?

(a) Chlorofluorocarbons
(b) Nitrous oxide
(c) Sulphur dioxide
(d) Carbon dioxide
Ans: (a) Chlorofluorocarbon contributes to ozone depletion in the upper atmosphere. It is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. Its manufacture has been phased out under the Montreal Protocol.

Q19. Chemical composition of heavy water is :

(a) H2O2 (b) H2O
(c) HDO (d) D2O
Ans: (d) The chemical composition of Heavy water (deuterium oxide) is 2H2O or D2O. It is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2H or D, also known as heavy hydrogen), rather than the common hydrogen-1 isotope (1H or H, also called protium) that makes up most of the hydrogen in regular water.

Q20. Oxide of sulphur present in the atmosphere are washed down by rains to cause :

(a) Depletion of fossil fuel reserves
(b) Eutrophication in lakes
(c) Lowering of pH of soil
(d) Industrial smog formation
Ans: (a) The oxide of Sulphur (Sulphur Dioxide) is washed down on earth as acid rain. It makes the soil acidic by lowering its pH; this affects plants and animals adversely. Acid rain contains H+, SO4 2- ions which when added to the soil leaches the nutrients from the soil. Acid rain renders the river or even ocean water acidic, thereby affecting marine animals adversely. Changes in pH of fresh water affect the reproduction and survival or many species or fish.

Q21. The acid which fails to liberate carbon dioxide from sodium bicarbonate is :

(a) Acetic acid
(b) Formic acid
(c) Carbonic acid
(d) Sulphuric acid
Ans: (d) Sodium bicarbonate and organic acid (Formic acid, Acetic acid, Carbonic acid, etc) react vigorously to liberate carbon dioxide. For example, Sodium bicarbonate (NaHCO3) when treated with acetic acid reacts vigorously to liberate carbon dioxide. NaHCO3 + CH3COOH CH3COONa + H2O + CO2

Q22. Which one of the following is not coal variety?

(a) Lignite (b) Bituminous
(c) Dolomite (d) Peat
Ans: (c) Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate with a chemical composition of CaMg(CO3)2. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. Dolomite is used in the Pidgeon process for the production of magnesium.

Q23. Dry ice is the solid form of :

(a) Air
(b) Carbon di–oxide
(c) Nitrogen (d) Water
Ans: (b) Dry ice, sometimes referred to as “cardice,” is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue. It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable.

Q24. The common name of sodium bicarbonate is

(a) Soda ash (b) Baking soda
(c) Soda lime (d) Baking powder
Ans: (b) Sodium bicarbonate (NaHCO3) is also known as baking soda, bread soda, cooking soda, and bicarbonate of soda. It is primarily used in cooking (baking), as a leavening agent. It reacts with acidic components in batters, releasing carbon dioxide, which causes expansion of the batter and forms the characteristic texture and grain in pancakes, cakes, quick breads, etc.

Q25. If there is one million Mg2+ ions in MgCl2, how many chloride ions are there?

(a) Two million (b)One million
(c) Half a million (d) Ten million
Ans: (a) Using formula of Stoichiometry, 1mol MgCl2 : 1mol Mg2+: 2mol Cl-. There are two moles of chloride ions for every one mole of MgCl2. So if there is one million Mg2+ ions in MgCl2, there will be two million chloride ions in it.

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