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Part 071 – Chemistry Previous Year Questions

Q1. Which of the following has pH value 7?
(a) Pure Water
(b) H2SO4
(c) Sodium Carbonate
(d) HCl
Ans: (a) In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, being neither an acid nor basic; so it has pH value of 7.

Q2. When ice cubes are made, the entropy of water

(a) does not change
(b) decreases
(c) increases
(d) may either increase or decrease depending on the process used
Ans: (b) When water is frozen into ice, the temperature drops below 0°C. Since the entropy of the solid is less than that of the liquid, the entropy of the water (the system here) will decrease on freezing. The amount of decrease is found by dividing the heat of fusion of ice by the temperature for the reversible pathway.

Q3. The compound used in pricklyheat powder to prevent excessive sweating is

(a) Boric acid
(b) Phosphoric acid
(c) Carbonic acid
(d) Sulphonic acid
Ans: (a) Boric acid (H3BO3), also called hydrogen borate, boracic acid, orthoboric acid and acidum boricum, is used in prickly heat powders to prevent excessive sweating. Boric acid is also used as an antiseptic for minor burns or cuts and is sometimes used in dressings or salves. As an antibacterial compound, boric acid can also be used for acne treatment.

Q4. Iron and manganese present as pollutants in water cannot be removed by_____

(a) oxidation followed by settling and filtration
(b) chlorination
(c) ion exchange process
(d) lime soda process or manganese zeolite process
Ans: (b) Water chlorination is the process of adding chlorine or hypochlorite to water. This method is used to kill certain bacteria and other microbes in tap water as chlorine is highly toxic. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, typhoid etc.

Q5. The antiparticle of an electron is

(a) Positron
(b) Proton
(c) Alpha particles
(d) Beta particles
Ans: (a) Corresponding to most kinds of particles, there is an associated antiparticle with the same mass and opposite charge (including electric charge). The antiparticle of the electron is the positron (antielectron), which has positive charge and is produced naturally in certain types of radioactive decay. The opposite is also true: the antiparticle of the positron is the electron.

Q6. Chemical properties of isotopes

(a) must be same
(b) must be different
(c) need not be same
(d) need not be different
Ans: (a) Isotopes of an element have similar chemical properties as they have the same number of electrons as an atom of that element. The electron arrangement is the same owing to same chemical properties. However, they have different numbers of neutrons, which affects the mass number. Mass number determines the physical properties such as boiling/melting/density etc.

Q7. Sour taste of lemon is due to the presence of which of the following ?

(a) Citric acid (b) Acetic acid
(c) Oxalic acid (d) Formic acid
Ans: (a) Lemon juice is about 5% citric acid, which gives lemons a sour taste and a pH of 2 to 3.Citric acid is found in many fruits but lemon contains large quantity of citric acid. The distinctive sour taste of lemon juice makes it a key ingredient in drinks and foods such as lemonade and lemon meringue pie.

Q8. Glycol is used to manufacture which of the following ?

(a) Nylon (b) Artificial silk
(c) Terylene (d) Rubber
Ans: (c) Monoethylene glycol (MEG), also known as ethylene glycol (EG) or simply glycol, is a diol mostly used for the production of polyester fibers and polyethylene terephthalate (PET) resins. Polyethylene terephthalate is used to produce textiles, large soft-drink containers, photographic film, and overhead transparencies. It is marketed under various trademarks including DACRON, Terylene, Fortrel, and Mylar.

Q9. During fermentation of sugar, the compound which is always formed is :

(a) Methyl Alcohol
(b) Ethyl Alcohol
(c) Acetic Acid
(d) Ethylene
Ans: (b) Fermentation is the conversion of sugar into carbon dioxide gas (CO2) and ethyl alcohol. This process is carried out by yeast cells using a range of enzymes. The overall process of fermentation is to convert glucose sugar (C6H12O6) to alcohol (CH3CH2OH) and carbon dioxide gas (CO2). C6H12O6 2 C2H5OH + 2 CO2+ Energy (which is stored in ATP).

Q10. Removal of carbon particles from air involves the principle of

(a) Precipitation
(b) Filteration
(c) Electrophoresis
(d) Sedimentation
Ans: (c) Carbon particles in air are colloidal in nature and carry negative charge. The removal of carbon particles from air involves the principle of electrophoresis. Carbon particles get precipitated by losing their charge and, thus, the air which finally comes out is free from them.

Q11. Which of the following acts as best adsorbent?

(a) Charcoal
(b) Activated Charcoal
(c) Activated Coconut Charcoal
(d) Carbon black
Ans: (c) Activated coconut charcoal is a highly absorbent material with millions of tiny pores that can capture, bind, and remove unwanted materials. The porous surface has a negative electric charge that attracts positively charged toxins and gas to be carried easily out of the body. It is used medicinally as well as in air and water purifiers.

Q12. Which of the following is used as non-stick coating for cooking utensils?

(a) Perspex (b)Styrofoam
(c) Polystyrene (d)Teflon
Ans: (d) The non-stick coating used mainly for coating cooking utensils is made using PTFE (polytetrafluoroethylene) that is also known by the name Teflon. Teflon is an inert polymer with high thermal and chemical resistance. Besides, it is hydrophobic: neither water nor water-containing substances wet it and it has one of the lowest coefficients of friction of any solid.

Q13. Particulates (< 1 μm size) remaining suspended in air indefinitely and transported by wind currents are called

(a) Mists (b) Fumes
(c) Aerosols (d) Smoke
Ans: (c) An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. The liquid or solid particles have diameter mostly smaller than 1 μm. They remain suspended in air for longer periods of time are transported to distances by winds. The finer particles could also be more easily re-suspended by subsequent wind action.

Q14. The least preferred technique in the disposal of Municipal Solid Waste is

(a) Incineration (b) Composting
(c) Land filling (d) Bricketting
Ans: (d) Some of the methods of solid waste disposal and management are : l Open burning l Dumping into the sea l Sanitary Landfills l Incineration l Composting l Ploughing in fields l Hog feeding l Grinding and discharging into sewers l Salvaging l Fermentation and biological digestion Bricketting that involves the solidification of preprocessed municipal solid waste into fuel pellets or briquettes is the least preferred method of solid waste disposal.

Q15. Which one of the following takes place during a nuclear fusion?

(a) a heavy nucleus bombarded by neutrons breaks up
(b) a heavy nucleus breaks up spontaneously
(c) two light nuclei combine to form a heavy nucleus
(d) a light nucleus breaks up spontaneously
Ans: (c) Nuclear fusion is the process of making a single heavy nucleus (part of an atom) from two lighter nuclei.The difference in mass between the products and reactants is manifested as the release of large amounts of energy. Fusion is the process that powers active or “main sequence” stars, or other high magnitude stars.

Q16. Of the following commonly used materials, the one that is not an alloy is

(a) Steel (b) Brass
(c) Bronze (d) Copper
Ans: (d) Copper is not an alloy; it is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. It is used as a constituent of various metal alloys, such as sterling silver used in jewellery, cupronickel used to make marine hardware and coins, and constant an used in strain gauges and thermocouples for temperature measurement. The alloys are:– l Steel is an alloy of iron and other elements, primarily carbon; l Brass is a metal alloy made of copper and zinc; l Bronze is an alloy consisting primarily of copper, commonly with about 12% tin.

Q17. Nitrogen fixation is a process of

(a) Assimilation of nitrate
(b) Utilisation of nitrogen gas
(c) Conversion of organic nitrogen to proteins
(d) Conversion of molecular nitrogen to ammonia
Ans: (d) Nitrogen fixation is a process by which nitrogen in the Earth’s atmosphere is converted into ammonia (NH3) or other molecules available to living organisms. Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. The fixation process frees nitrogen atoms from their triply bonded diatomic form, NN, to be used by plants as nutrients. The conversion of organic nitrogen to proteins is achieved in Nitrogen cycle.

Q18. Bronze is an alloy of

(a) Copper & tin
(b) Copper & zinc
(c) Copper & iron
(d) Iron & nickel
Ans: (a) Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as aluminium, manganese, nickel or zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties.

Q19. Which acid is used in Lead storage battery?

(a) Sulphuric acid
(b) Nitric acid
(c) Hydrochloric acid
(d) Acetic acid
Ans: (a) Lead acid battery is a storage battery or secondary battery in which electrical energy can be stored as chemical energy and this chemical energy is then converted to electrical energy as when required. Leadacid batteries are composed of a Lead-dioxide cathode, a sponge metallic Lead anode and a Sulphuric acid solution electrolyte.

Q20. Two electrons in an orbital are differentiated by which of the following ?

(a) Magnetic quantum number
(b) Spin quantum number
(c) Principal quantum number
(d) Azimuthal quantum number
Ans: (b) Spin quantum number is the is the fourth quantum number that differentiates two electrons in the same orbital. The Pauli exclusion principle states that “no two electrons in an atom can have the same four quantum numbers. This means that no two electrons can have the same state in an atom. Each electron must have a different spin or occupy a different shell from any other.

Q21. The most abundant element in the earth’s atmosphere is

(a) Argon (b) Nitrogen
(c) Oxygen (d) Krypton
Ans: (b) The most abundant gas in the Earth’s atmosphere is nitrogen. Nitrogen makes up 78 percent of the Earth’s atmosphere, and it is a permanent gas, which means that its percentage does not change on a daily basis. The rest of the atmosphere is made up of 21 percent oxygen, 0.9 percent argon and 0.1 percent trace gases.

Q22. Chemical composition of cement is

(a) Limestone and Clay
(b) Limestone, Clay and Gypsum
(c) Limestone and Gypsum
(d) Clay and Gypsum
Ans: (b) The two important raw materials used for the preparation of cement are : l Limestone : The chemical formula of limestone is CaCO3 and it is used in the manufacture of cement just to provide CaO. l Clay : Clay is hydrated aluminium silicate and iron (iii) oxide having chemical formula Al2O3SiO2Fe2O3.2H2O. Thus, clay consists of aluminium oxide (Al2O3), silicon dioxide (SiO2), and iron (iii) oxide (Fe2O3) along with water molecules. In addition of limestone and clay, gypsum is also used during preparation of cement. It is added into the cement to slow down the hardening of cement when water is added into it.

Q23. Which of the following is also used as a Bio fertilizer?

(a) Urea (b) Ammonia
(c) Uric Acid (d) Nitrates
Ans: (*) A Bio fertilizer is a substance which contains living microorganisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Rhizobium, Azotobacter, Azospirillum and blue green algae are traditionally used as Biofertilizers. Best Option : (b) Ammonia occupies an unique biochemical position being the only inorganic form of nitrogen that is incorporated into organic linkage and thus an obligate intermediate in the utilization of other inorganic sources.

Q24. ____ is used for making vinegar.

(a) Tartaric acid
(b) Malic acid
(c) Oxalic acid
(d) Acetic acid
Ans: (d) Vinegar is a liquid consisting mainly of acetic acid (CH3COOH) and water. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria. It is mainly used as a cooking ingredient.

Q25. Major portion of the earth’s crust is mainly constituted by

(a) Oxygen and Iron
(b) Oxygen and Silicon
(c) Silicon and Iron
(d) Silicon and Aluminium
Ans: (b) Oxygen is the most abundant element in the earth’s crust, comprising 46.6% or the crust by weight. Silicon 28%, aluminum 8.2%, iron 5.6%, calcium 4.2%, sodium 2.5%, magnesium 2.4%, potassium, 2.0%, and titanium 0.61% also comprise the crust. Given the abundance of oxygen and silicon, the silicates are the most abundant minerals in the earth’s crust.

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