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Part 064 – Chemistry Previous Year Questions

Q1. If the equilibrium constants for the systems H2 + I2 2HI and 2HI H2 + I2 are K1 and K2 respectively, the relationship between K1 and K2 is :
(a) K1 = K2 (b) K1 = 2K2
(c) K1 = 2/2 (d) K1 = 1/K2
Ans: (d) As per the Law of Mass Action, if Kf is the equilibrium constant for the equation A + B C + D, then 1/Kf is the equilibrium constant for the reverse equation, C + D A + B. So, as per the question K1 is the equilibrium constant for H2 + I2 2 HI, then 1/K1 is equilibrium constant for the reverse equation 2 HI H2 + I2

Q2. Concentration of a material which is lethal to 50% animal is called

(a) LD50 (b) LC50
(c) NOAEL (d) ADI
Ans: (a) LD50 (Lethal Dose 50) is the amount of a solid or liquid material that it takes to kill 50% of test animals (for example, mice or rats) in one dose. LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. LC50 is the concentration of a material in air that will kill 50% of the test subjects when administered as a single exposure.

Q3. Muddy water is treated with alum in purification process, itis termed as :

(a) emulsification (b)absorption
(c) adsorption (d) coagulation
Ans: (d) Natural and wastewater contain small particulates that are suspended in water forming a colloid. These particles carry the same charges, and repulsion prevents them from combining into larger particulates to settle. Historically, dirty water is cleaned by treating with alum, Al2(SO4)3.12 H2O, and lime, Ca(OH)2. The phenomenon is known as coagulation: Al 2 (SO 4 ) 3 .12 H2O Al(aq)3+ + 3SO4(aq)2- + 12H2O SO4(aq)2- + H2O HSO4(aq)- + OH- (causing pH change) Ca(OH)2 Ca(aq)2+ + 2 OH- (causing pH change) The slightly basic water causes Al(OH)3, Fe(OH)3 and Fe(OH)2 to precipitate, bringing the small particulates with them and the water becomes clear.

Q4. Brass contains

(a) Copper and Zinc
(b) Copper and Tin
(c) Copper and Silver
(d) Copper and Nickel
Ans: (a) Brass is an alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. By comparison, bronze is principally an alloy of copper and tin.

Q5. Which is the purest commercial form of iron ?

(a) Pig iron
(b) Steel
(c) Stainless steel
(d) Wrought iron
Ans: (d) Wrought iron or malleable iron is the purest form of commercial iron as it contains the lowest percentage of carbon (0.12-0.25%) and impurities of S, P, Mn and Si in minute amount (about 0.3%). It is made by melting cast iron with scrap iron in a reverberatory furnace lined with Fe2O3 which oxidizes C, Si, P, etc, most of which are then removed by rolling.

Q6. In galvanization, iron is coated with

(a) Copper (b) Zinc
(c) Tin (d) Nickel
Ans: (b) Galvanization is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanization, in which parts are submerged in a bath of molten zinc.

Q7. Which one of the folling is also khow as solution ?

(a) A compound
(b) A homogeneous mixture
(c) A heterogeneous mixture
(d) A suspension
Ans: (b) In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The solution more or less takes on the characteristics of the solvent including its phase.

Q8. A solution is

(a) a homogeneous mixture of two or more substances
(b) a solid dissolved in a liquid
(c) a solid dissolved i water
(d) a mixture of two liquids
Ans: (a) A homogeneous mixture of two or more substances uniformly dispersed throughout a single phase is called solution. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The solution more or less takes on the characteristics of the solvent including its phase, and the solvent is commonly the major fraction of the mixture.

Q9. The first organic compound synthesised in the laboratory was

(a) Urea (b) Uric acid
(c) Lactic acid (d) Glucose
Ans: (a) In 1828, German chemist Friedrish Wohler synthesized first organic compound, urea in the laboratory by heating ammonium cyanate (an inorganic compound). NH4CNO (Ammonium Cyanate) NH2CONH2 (Urea) Soon, Kolbe, in 1845, synthesized Acetic acid in laboratory from Carbon, Hydrogen and Oxygen.

Q10. Which one of the following contains maximum percentage of carbon ?

(a) Cast iron
(b) Stainless steel
(c) Wrought iron
(d) High speed steel
Ans: (a) Cast Iron is a hard, brittle, nonmalleable iron-carbon alloy, cast into shape, containing 2 to 4.5 percent carbon. Steels contain less than 2% and usually less than 1% carbon, while all cast irons contain more than 2% carbon. Most steel contains less than 0.35 percent carbon. Wrought iron is an iron alloy with very low carbon (0.04 to 0.08%) content.

Q11. Which of the following appeared to be with a significant potential for accumulation through food chains ?

(a) DDT (b) Parathion
(c) Lindane (d) Carbary
Ans: (a) Mercury and DDT are two persistent toxic materials that accumulate in the food chain and damage the organisms in it. DDT is an insecticide that can pass up the food chain from insects to small birds, and then from the small birds to birds of prey. It is now banned because of this.

Q12. Which one of the following elements is an example of noble gas ?

(a) Nitrogen (b) Hydrogen
(c) Chlorine (d) Helium
Ans: (d) Noble gas refers to any of the seven chemical elements that make up Group VIIIa of the periodic table. The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and element 118 (temporarily named ununoctium (Uuo)).

Q13. Which of the following elements does not exhibit natural radioactivity ?

(a) Uranium (b) Thorium
(c) Aluminium (d) Polonium
Ans: (c) Uranium, Thorium and Polonium are radioactive elements which do not have stable naturally occurring isotope. Aluminium is a silvery white, soft, ductile metal. It is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth’s crust.

Q14. The most abundant element is

(a) Calcium (b) Silicon
(c) Oxygen (d) Nitrogen
Ans: (c) On earth, oxygen is the most common element, making up about 47% of the earth’s mass. Silicon is second, making up 28%, followed by aluminum (8%), iron (5%), magnesium (2%), calcium (4%), sodium (3%), and potassium (3%). All of the remaining elements together make up less than 1% of the earth’s mass.

Q15. Aluminium salt commonly used to stop bleeding is

(a) Aluminium nitrate
(b) Aluminium sulphate
(c) Aluminium Chloride
(d) Potash alum
Ans: (b) Alum (Aluminium Sulfate) is used to stop bleeding. For example, Styptic pencils containing aluminium sulfate are used as astringents to prevent bleeding from small shaving cuts. It constricts blood vessels to stop the flow of blood.

Q16. Nitrogen in water is commonly found in the form of

(a) Nitrous oxide (b)Nitrate
(c) Nitric oxide (d)Nitrite
Ans: (b) Nitrate (NO3) is the most common form of inorganic nitrogen in unpolluted waters. Nitrate moves readily through soils and into ground water, where concentrations can be much higher than in surface waters. Water in coastal areas mainly contains elementary nitrogen gas (N2).

Q17. Chemical name of Gammaxane is

(a) Toluene
(b) Chloro benzene
(c) Aniline
(d) Benzene hexachloride
Ans: (d) Gammexane is an insecticide that is the gamma isomer of benzene hexachloride. It is also known as lindane. Benzene hexachloride is any of several stereoisomers of 1,2,3,4,5,6-hexachlorocyclohexane formed by the light-induced addition of chlorine to benzene.

Q18. Which element behaves chemically both as metal and nonmetal ?

(a) Argon (b) Boron
(c) Xenon (d) Carbon
Ans: (b) Some elements behave chemically both as metals and nonmetals, and are called metalloids. Their examples include Boron, Silicon, Germanium and Antimony. Elements which are neither metals nor nonmetals are called Noble Gases.

Q19. The amount of oxygen in the atmosphere remains relatively constant because it is given off by

(a) Oceans (b) Animals
(c) Rocks (d) Plants
Ans: (d) Just as water moves from the sky to the earth and back in the hydrologic cycle, oxygen is also cycled through the environment. Plants mark the beginning of the oxygen cycle. They use the energy of sunlight to convert carbon dioxide and water into carbohydrates and oxygen in a process called photosynthesis. O2 + Carbohydrates CO2 + H2O + Energy This means that plants “breathe” in carbon dioxide and “breathe” out oxygen.

Q20. Water gas is the combination of

(a) CO and H2 (b)CO2 and H2
(c) CO and H2O(d)CO2 and CO
Ans: (a) Water gas is a synthesis gas, containing carbon monoxide (CO) and hydrogen gas (H2). It is made by passing steam over a red-hot carbon fuel such as coke. The reaction between steam and hydrocarbons produce the gas mixture.

Q21. Which of the following elements is obtained from sea weeds ?

(a) Iodine (b) Vanadium
(c) Argon (d) Sulphur
Ans: (a) Seaweed is rich in iodine, a trace element essential for healthy thyroid function and a healthy metabolism. Iodine is particularly vital for pregnant and lactating women. Seaweed also contains zinc and antioxidants, which help strengthen immunity.

Q22. Acid Rain is caused due to pollution of atmosphere by

(a) Oxides of nitrogen and phosphorus
(b) Oxides of carbon and nitrogen
(c) Oxides of nitrogen and sulphur
(d) None of these
Ans: (c) Acid rain is caused by emissions of oxides of Sulfur and Nitrogen (Sulfur Dioxide and Nitrogen Oxide), which react with the water molecules in the atmosphere to produce acids. The emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) result from fossil fuel combustion.

Q23. Carbon footprint can be reduced by

(a) All of these
(b) Recycling waste materials
(c) Using energy efficient appliances
(d) Commuting by public transport
Ans: (a) A carbon footprint is historically defined as “the total sets of greenhouse gas emissions caused by an organization, event, product or person.” The most common way to reduce the carbon footprint of humans is to Reduce, Reuse, Recycle, Refuse. Recycling waste materials, using energy efficient appliances and using public transportation for commutation can all serve to reduce greenhouse gas emissions and, thus, reduce Carbon footprint.

Q24. Which one of the following is found in Vinegar ?

(a) Acetic acid
(b) Propionic acid
(c) Formic acid
(d) Butyric acid
Ans: (a) 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. Peroxyacetyl nitrate is a

(a) Acidic dye
(b) Plant hormone
(c) Vitamin
(d) Secondary pollutant
Ans: (d) Peroxyacetyl nitrate is a secondary pollutant present in photochemical smog (a mixture of air pollutants) that includes both gases and particulates. It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas. It is a lachrymatory substance.

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