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Part 069 – Chemistry Previous Year Questions

Q1. Which of the process is known as nitrification?
(a) Reaction of Nitrogen Monoxide with oxygen to form nitric acid
(b) Reaction of nitrogen dioxide with water to form nitric acid
(c) Conversion of ammonia to nitrites
(d) Conversion of nitrite to nitric oxide
Ans: (c) Nitrification is the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. The oxidation of ammonia into nitrite is performed by two groups of organisms, ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Nitrification is an important step in the nitrogen cycle in soil.

Q2. The purest form of water in nature is

(a) Rain water (b) Lake water
(c) River water (d) Sea water
Ans: (a) Rainwater is often considered the purest form of water available on the Earth. The evaporation of water by the sun allows the salts and other impurities to be left behind out of the water. However, in reality, rain water is often much less than pure when it reaches the surface of the Earth due to the high pollution of air with toxic gases.

Q3. The source of energy that causes the least global warming is

(a) Coal
(b) Geothermal energy
(c) Natural Gas
(d) Petroleum
Ans: (c) Fossil fuels — coal, petroleum, and natural gas — are the primary culprit behind climate change. They contribute more than 80 percent of greenhouse gas emissions — and 98 percent of CO2 emissions alone. On the contrary, Geothermal energy is thermal energy generated and stored in the Earth. It is clean and sustainable.

Q4. Which of the following is not a donor atom?

(a) Phosphorus (b) Antimony
(c) Arsenic (d) Aluminium
Ans: (d) Aluminium is an acceptor atom, an impurity atom in a semiconductor, which can accept or take up one or more electrons from the crystal and become negatively charged.In semiconductor physics. It is a dopant atom that when added to a semiconductor can form a p-type region. For example, when silicon (Si), having four valence electrons, needs to be doped as a p-type semiconductor, elements from group III like boron (B) or aluminium (Al), having three valence electrons, can be used. The latter elements are also called trivalent impurities. Other trivalent dopants include indium (In) and gallium (Ga).

Q5. Besides CO2, the other green house gas is

(a) CH4 (b) N2 N2
(c) Ar Ar (d) O2
Ans: (a) The greenhouse gases in Earth’s atmosphere are: Water vapour (H2O), Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Ozone (O3) and Chlorofluorocarbons (CFCs). Methane is an important greenhouse gas with a global warming potential of 34 compared to CO2 over a 100-year period, and 72 over a 20-year period.

Q6. Which of the following is a commercial source of energy?

(a) Agricultural waste
(b) Dried dung
(c) Sun
(d) Natural gas
Ans: (d) Energy is broadly classified as commercial and non-commercial energy. Firewood, agricultural waste (straw, etc.) and animals waste (cowdung) are the important components of non-commercial energy.Coal, petroleum products, natural gas and, electricity are the important components of commercial energy. These goods are largely used for commercial purposes in the factories and farms.

Q7. Which of the following is a natural polymer?

(a) Bakelite (b) Nylon
(c) Polythene (d) Starch
Ans: (d) Cotton, starch, cellulose and rubber are some of the naturally occurring polymers.Starch is a condensation polymer made up of hundreds of glucose monomers, which split out water molecules as they chemically combine. Starch is a member of the basic food group carbohydrates and is found in cereal grains and potatoes. It is also referred to as a polysaccharide, because it is a polymer of the monosaccharide glucose.

Q8. Which one of the following nonmetals shows allotropy in the liquid state?

(a) Carbon
(b) Sulphur
(c) Phosphorous
(d) Bromine
Ans: (b) Sulphur is a non-metal that shows allotropy in the liquid state. If sulphur is heated slowly the changes between the different forms can be observed. These changes are in the form of colour and viscosity (thickness) of the liquid. If the dark brown liquid sulphur is poured into a beaker of cold water, plastic sulphur is formed. This is an elastic, rubber-like form of sulphur.

Q9. Which of the following is not a nitrogenous fetiliser?

(a) Ammonium sulphate
(b) Urea
(c) Ammonium nitrate
(d) Superphosphate
Ans: (d) Superphosphateis a common synthetic phosphorus fertilizer. It contains phosphorus and sulphur in a ratio of 1 to 1.22.?It is produced by treatment of “phosphate rock” with acids such as sulphuric acid. Superphosphate is the principal carrier of phosphate, the form of phosphorus usable by plants, and is one of the world’s most important fertilizers.

Q10. Bauxite is used as raw material by which industry ?

(a) Aluminium (b) Iron
(c) Steel (d) Gold
Ans: (a) Bauxite is the principal ore of aluminium. Bauxite is not a mineral. It is a rock formed from a laterite soil that has been severely leached of silica and other soluble materials in a wet tropical or subtropical climate. Aluminium is extracted from bauxite using the Bayer process.

Q11. Thermal electricity is generated by using which of these ?

(a) Coal only
(b) Coal and Natural Gas only
(c) Coal, Natural Gas and Petroleum
(d) None of these
Ans: (c) A thermal power station is a power plant in which heat energy is converted to electric power. Thermal power is producing using fossil fuel such as coal, natural gas or petroleum. More than 65% of India’s electricity generation capacity comes from thermal power plants, with about 85% of the country’s thermal power generation being coal-based.

Q12. When iron rusts, its weight

(a) decreases
(b) increases
(c) remains the same
(d) first increases and then decreases
Ans: (b) When iron rusts, oxide compounds are formed due the interaction between oxygen in the air or in water and the metal. Because of the oxygen atoms binding with the metal, the weight of the metal with rust will increase.

Q13. Silver gets corroded due to ___ in air.

(a) Oxygen
(b) Hydrogen Sulphide
(c) Carbon dioxide
(d) Nitrogen
Ans: (b) Silver is a fairly stable metal and under normal circumstances does not corrode quickly. However, it is particularly susceptible to the effects of the sulfide radical. However, when exposed to air, silver reacts with Hydrogen Sulphide in the atmosphere, especially in marine environment, and readily forms a surface tarnish of silver sulphide. 2Ag + H2S Ag2S +H2

Q14. Which of the following is a radioactive element?

(a) Cobalt (b) Uranium
(c) Argon (d) Chromium
Ans: (b) Uranium (U) is a naturally occurring radioactive element. Its nucleus is unstable, so the element is in a constant state of decay, seeking a more stable arrangement. One of its isotopes, uranium-235, is the only naturally occurring isotope capable of sustaining a nuclear fission reaction.In fact, uranium was the element that made the discovery of radioactivity possible.

Q15. Ozone saves the biosphere by absorbing high energy radiations called _____ .

(a) Infra-red (IR)
(b) Gamma rays
(c) Ultraviolet rays (UV)
(d) X–rays
Ans: (c) The ozone layer or ozone shield is a region of Earth’s stratosphere that absorbs most of the Sun’s ultraviolet (UV) radiation. It absorbs 97 to 99 percent of the Sun’s medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms near the surface.

Q16. Silica gel is a

(a) moisturizer
(b) flavouring agent
(c) drying agent
(d) delicious food
Ans: (c) Silica gel is a drying agent, meant to remove moisture from an enclosed space. It is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate.Silica gel packs are found in boxes containing electronics or new shoes and inside purses or medicine bottles. The packets contain either granular silicic acid, which resembles sand, or tiny gel beads.

Q17. Biofertilizers convert nitrogen to _______ .

(a) nitrates (b) ammonia
(c) nitrogenase (d) amino acids
Ans: (b) Bio-fertilizers are micro-organisms which bring about nutrient enrichment of soil by enhancing the availability of nutrients to crops. The micro-organisms which act as bio-fertilizers are bacteria, cyanobacteria (blue green algae) and mycorrhizal fungi.The symbiotic nitrogen-fixing bacteria convert free nitrogen to ammonia, which the host plant utilizes for its development.

Q18. All isotopes of the same element have ______

(a) different atomic numbers and different atomic mass
(b) different atomic numbers and the same atomic mass
(c) the same atomic number but different atomic masses
(d) the same atomic number and the atomic mass
Ans: (c) Isotopes are forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei. So they have the same atomic number, but differ in relative atomic mass. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon having the same atomic number of 6, but with mass numbers 12, 13 and 14 respectively.

Q19. Nitric acid does not react with

(a) Gold (b) Copper
(c) Zinc (d) Iron
Ans: (a) Concentrated nitric acid is a very strong oxidator capable of reacting with the noble metals such as copper or silver. Some precious metals, such as pure gold and platinum-group metals do not react with nitric acid. However, pure gold does react with aqua regia, a mixture of concentrated nitric acid and hydrochloric acid.

Q20. In arc welding, Argon is used because of its

(a) Low reactivity with metal
(b) Ability to lower the melting point of the metal
(c) High flammability
(d) High calorific value
Ans: (a) In arc welding, Argon is used as a shielding gas because it is chemically inert and forms no compounds. At the high temperatures that welding requires, the metals being welded become highly reactive to the elements in the atmosphere. Contamination from these elements can lead to brittle welds and instability in the welding arc. So,argon and other inert gases are sprayed.

Q21. Inert gases are

(a) Miscible with water
(b) Not stable
(c) Chemically unreactive
(d) Chemically very active
Ans: (c) An inert gas is a gas which does not undergo chemical reactions since their valence shells are filled, meaning they don’t normally form chemical bonds with other elements. They are extremely stable; they rarely gain, lose or share electrons.The inert gases, also called noble gases, are argon, helium, neon, krypton, xenon and radon.

Q22. Chemical name of vinegar is

(a) Acetone (b) Acetic acid
(c) Formaldehyde
(d) Ethanol
Ans: (b) Vinegar is roughly 3–9% acetic acid CH3COOH) by volume, making acetic acid the main component of vinegar apart from water. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria.Vinegar is mainly used as a cooking ingredient, or in pickling.

Q23. Iodex, a pain relief balm, has the smell of __________ .

(a) Methyl salicylate
(b) Ethyl salicylate
(c) Propyl salicylate
(d) Butyl salicylate
Ans: (a) Iodex has the characteristic odour of Methyl salicylate, an organic ester naturally produced by many species of plants, particularly wintergreens. It is used in high concentrations as a rubefacient and analgesic in deep heating liniments to treat joint and muscular pain.

Q24. Which of the following is usually not an air-pollutant?

(a) Hydrocarbons
(b) Sulphur dioxide
(c) Carbon dioxide
(d) Nitrous oxide
Ans: (d) The six air pollutants are carbon monoxide, lead, ground-level ozone, nitrogen dioxide, particulate matter, and sulfur dioxide.The combustion of gasoline and other hydrocarbon fuels in automobiles, trucks, and jet airplanes produces several primary air pollutants. Nitrous oxide (N2O), commonly known as laughing gas, is used in surgery and dentistry for its anaesthetic and analgesic effects.

Q25. Which of the following fuels causes minimum environmental pollution?

(a) Diesel (b) Kerosene
(c) Hydrogen (d) Coal
Ans: (c) Coal, diesel and kerosene are examples of fossil fuels that contribute to pollution. In contrast, hydrogen burns in air, it produces nothing but water vapor and energy. It is considered as totally clean and nonpolluting source of energy.

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