Chemistry – Science – WBCS Main Question Paper

Chemistry - Science - WBCS Main Question Paper
wbcs main chemistry question paper

WBCS Main Question Paper – 2019

9. The pH for drinking water should be between
(A) 5 – 6
(B) 6 – 6.5
(C) 6.5 – 7.5
(D) 8 – 9
105. The function of heavy water in a nuclear reactor is to
(A) cool down the reactor.
(B) stop the nuclear reaction.
(C) slow down the speed of neutrons.
(D) increase the speed of neutrons
106. The general molecular formula for disaccharide is
(A) C10H20O10
(B) C12H22O11
(C) C12H20O10
(D) C12H22O10
115. Which of the following configurations corresponds to element of highest ionization energy?
(A) 1S2, 2s1
{B) 1s2, 2s2, 2p3
(C) 1s2, 2s2, 2p2
(D) 1s2, 2s2, 2p6, 3s1
116. Oxidation state of Oxygen in F2O is
(A) -1
(B) +1
(C) +2
(D) -2
117. Which of the following does not have coordinate bond?
(A) SO2
(B) HNO2
(C) HNO3
(D) H2SO3
(A) C2H2
(B) C2H6
(C) C3H4
(D) C3H8
119. Which is used in alcoholic beverages?
(A) Ethanol
(B) Methanol
(C) Phenol
(D) Glycerol
138. For the radioactive nuclei that undergo either α or ß decay, which one of the following cannot occur?
(A) Isobar of original nucleus is produced.
(B) Isotope of the original nucleus is produce
(C) Nuclei with higher atomic number than that of the original nucleus is produced.
(D) Nuclei with lower atomic number than that of the original nucleus is produced.
140. During the emission of a positron from a nucleus, the mass number of the daughter element remains the same but the atomic number
(A) is decreased by 1 unit
(B) is decreased by 2 units
(C) is increased by 1 unit
(D) remains unchanged
141. Which one of the following is wrong about molecularity of a reaction?
(A) It may be whole number or fractional.
(B) It is calculated from reaction mechanism.
(C) It is the number of molecules of the reactants taking part in a single step chemical reaction.
(D) It is always equal to the order of elementary reaction.
161. The unit of radioactivity is
(A) Co
(B) Ci      (SI unit – curie )
(C) Cr
(D) Cq
165. The temporary hardness of water is caused by
(A) Oxides
(B) Bicarbonates
(C) Chlorides
(D) Sulphates
171. SiO2 is reacted with Sodium Carbonate. What is the gas liberated?
(A) CO2
(B) CO
(C) O2
(D) O3
174. In gamma ray emission from a nucleus
(A) only proton number changes.
(B) only neutron number changes.
(C) there is no change in the proton number and neutron number.
(D) Both the proton number and the neutron number change.
175. In radioactive decay process, the negatively charged emitted ß particles are
(A) the electrons present inside the nucleus.
(B) the electrons produced as a result of the decay of neutrons inside the nucleus.
(C) the electrons produced as a result of collisions between atoms.
(D) None of the above
186. What is the main energy generation process in the Sun?
(A) Nuclear fission
(B) Nuclear radioactive decay
(C) Gravitational energy
(D) Nuclear fusion
187. Formation of stars begin from the following two gases:
(A) Hydrogen and Nitrogen
(B) Nitrogen and Oxygen
(C) Oxygen and Hydrogen
(D) Hydrogen and Helium
177. Which of the following is a liquid form of aerosol?
(A) Fume
(B) Dust
(C) Mist
(D) Smoke



WBCS Main Question Paper – 2018

4. The organic compound used as food preservative :
a) Methyl salicylate
b) Sodium benzoate
c) Sodium acetate
d) Sorbitol
5. The isotope used in cancer therapy
a) Co58   
b) C14
c) I131     
d) Co60
6. Formula of baking powder is
a) NaHCO3
b) Na2CO3, 10H2O
c) Na2B4O7 ,10H2O
d) CaSO4, 2H2O
7. Carbon atom in benzene molecule is
a) sp hybridised
b) sp2 hybridised
c) sp3 hybridised
d) Not hybridised
8. The carbolic acid is
a) benzoic acid
b) phthalic acid
c) phenol
d) H2CO3
9. Which of the following heterocyclic compound is not aromatic ?
a) Pyridiene
b) Pyrole
c) Furan
d) Piperidine
10. The oxide functioning as Piezoelectric substance :
a) Al2O3   
b) ZrO2
c) TiO2      
d) BaTiO3
11. Which of the following is used as high temperature lubricant ?
a) Mica
b) Asbestos
c) Graphite
d) Silicones
12. Which of the following salt is dissolved in aqueous ammonia ?
a) PbCl2
b) Cu(OH)2
c) AgI
d) Al(OH)2
13. The reaction of Cl2 + 2NaOH = NaCl + NaOCl + H2O is a
a) subsitution reaction
b) elminiation
c) neutralisation reaction
d) disproportionation reaction
14. Graphite is used in nuclear reactor as
a) Lubricant
b) Fuel rod
c) Control rod
d) Coating
15. Black color of old oil painting can be cleaned by
a) Cl2 water
b) H2O2
c) Nascent hydrogen
d) Oxalic acid
16. Which is the hardest material of the following ?
a) Corundum
b) Diamond
c) SiC
d) B4C
17. NH3 gas is dried by using
a) Conc. H2SO4
b) P2O5
c) Fused CaCl2
d) Qucik Lime
18. In the contact process for the manufacture of H2SO4, V2O5 function as
a) oxidising agent
b) reducing agent
c) catalyst
d) neutralising agent
19. A thick mass of cement, sand and water is called
a) Concrete
b) RCC
c) Mortar
d) Monolith
20. Bronze is the alloy of
a) Copper and Zinc
b) Copper and Tin
c) Coper and Nickel
d) Zinc and Tin
21. The process of very slow cooling in metallurgy is known as
a) Quenching
b) Annealing
c) Hardening
d) Cold working
22. The metal extracted from hematite using blast furnace:
a) Zn    
b) Cu
c) Al      
d) Fe
23. The chemical bonding in diamond is
a) Covalent
b) Ionic
c) Coordinate
d) Metallic

24. For deriving p-type semiconductor, the element to be mixed with Si :
a) Phosphorous
b) Aluminum
c) Arsenic
d) None of the above
30. Which of the following is an artificial rubber ?
a) Isoprene
b) Chloroprene
c) Neoprene
d) Teflon
29. The connecting material in solar panels is
a) Si              
b) Silver
c) Selenium  
d) CuH.O
32. Phenol and Formaldehyde are used for the production of
a) Caprolactum
b) Bakelite
c) PVC
d) Nylon 6
33. Nucleons are the number of
a) protons present in the nucleus
b) neutrons present in the nucleus
c) sum of protons and neutrons in the nucleus
d) total protons, neutrons and electrons in the atom
34. Which of the following fuel produces hottest flame on ignition with oxygen ?
a) C2H2
b) H2
c) Cyanogen
d) Butane
38. When electricity is passed through an electrolyte it undergoes
a) physical changes
b) chemical changes
c) no physical or chemical changes
d) dissociation into cation and anion
40. Temperature (K) and volume (V) relationship of a gas undergoing adiabatic expansion  (y= Cp/Cv)
a) TV = Constant
b) TVy = Constant
c) TVy-1 = Constant
d) T yV = Constant
41. The crystal having cell dimensions, a ¹ B  ¹ c, a = b = g = 90º   has structure
a) Tetragonal
b) Orthorhombic
c) Triclnic
d) Monoclinc
74. Which of the following possesses zero dipole moment?
a) NH3   
b) CCl4
c) BF3    
d) H2O
57. If an enzyme fixes nitrogen in plant by evolving H2, the number of electrons and protons associated with respectively are
a) 6 and 6
b) 6 and 8
c) 8 and 8
d) 8 and 6
58. Water becomes hard due to presence of soluble salt of ion
a) Al+3   
b) Na
c) K         
d) Ca2+
71. Pressure Volume relation for a mono-atomic gas undergoing adiabatic expansion:
a) PV1/3 = Constant
b) PV 2/3= Constant
c) PV 4/3= Constant
d) PV 5/3= Constant
72. At 0 K, fluids are assumed to have
a) minimum entropy
b) maximum entropy
c) zero entropy
d) a fixed value of entropy
76. Water has maximum density at
a) room temperature
b) 0°C
c) 4°C
d) 100°C
77. The water used in nuclear reactor is called
a) Hard water
b) Heavy water
c) Nuclear water
d) Critical water
78. The quantity remaining constant in isothermal expansion of an ideal gas:
a) Heat content
b) Internal energy
c) Pressure
d) Pressure and Temperature
83. Water gas is extremely poisonous due to presence of
a) N2   
b) CO
c) H2   
d) H2S
86. The quality of gasolene is expressed in terms of
a) Octane number
b) Cetane number
c) Gold number
d) Reynold’s number
87. Which of the following is a complex salt?
a) A1(NO3)3,9H2O
b) K4[Fe(CN)6]
c) KSO4, Cr(SO4)3, 24 H2O
d) Ca(OCl)Cl
89. Which compound is used as rocket fuel?
a) Polybutadiene
b) N2H4
c) N3H
d) Both (A) and (B)
90. When molten sulphur is poured suddenly into water, it takes the form of
a) milk of sulphur
b) flower of sulphur
c) plastic sulphur
d) colloidal sulphur
91. The compound used in safety matches is
a) P4       
b) PCl3
c) P2O5   
d) P4S3
94. Permanent hardness of water is estimated by
a) Conductometne titration
b) lodometric titration
c) Acid-base titration
d) Complexometric EDTA titration
100. The gas used to extinguish fire:
a) CO2  
b) Ar
c) N2     
d) CO

WBCS Main Question Paper – 2017

62. Crude petroleum is converted to number of hydrocarbon products by
(A) Fractional distillation       
(B) Thermal cracking      
(C) Steam distillation      
(D) None of the above
65. The Redox indicator used in volumetric titration of
(A) Bromophynol Blue
(B) Methyl Orange
(C) Barium diphenyl amine sulphonate
(D) Solochrome black-T
99. Gas released during Bhopal tragedy was :
(A) Sodium isothiocyanate
(B) Ethyl isothiocyanate
(C) Potassium isothiocyanate
(D) Methyl isothiocyanate
101. Natural rubber is a polymer of
(A) Isoprene       
(B) Styrene        
(C) Vinyl acetate      
(D) Butadiene
102. Tollens reagent is
(A) Alkaline mercuric chloride
(B) Alkaline potassium permanganate
(C) Ammoniacal silver nitrate
(D) Ammonium citrate
103. Paraffin wax is
(A) Ester      
(B) Alcohol       
(C) unsaturated hydrocarbons      
(D) saturated hydrocarbons
104. Which one of the following gas is used for artificial ripening of fruits ?
(A) Methane        
(B) Acetylene        
(C) Ethylene       
(D) Propane
105. Which one of the following materials does not show piezoelectric behavior ?
(A) Quartz        
(B) Rochelle salt       
(C) Rutile       
(D) Barium titanate
106. The melting point of silica is
(A) 1710° C       
(B) 2050°C       
(C) 2300°C        
(D) 1810°C
107. The BET study is performed to measure
(A) particle size distribution       
(B) specific surface area       
(C) dielectric constant      
(D) specific gravity

108. The potash feldspar is known as
(A) Orthoclase       
(B) Albite       
(C) Anorthite      
(D) Dickite
109. The acid employed for etching of glass is
(A) HCl      
(B) HNO3       
(C) Aqua-regia        
(D) HF
110. Which one of the following remains in solid state at room temperature ?   
(melting point 113.7 °C)
(A) Cl2      
(B) F2        
(C) I2      
(D) Br2
111. Mars gas contains
(CO2 – 95.32%, N2 – 2.6%, Ar – 1.9%)
(A) CO2        
(B) CH4       
(C) N2       
(D) C2H6
112. Which one of following constitutes the common glass composition ?
(A) Sodium Silicate     
(B) Calcium Silicate      
(C) Calcium and Sodium Silicate      
(D) Lead Silicate
113. Stainless steel contains
(A) Fe + Cr + Ni      
(B) Fe + Ni + Cu       
(C) Fe + Mn + Cr      
(D) Fe + Co + Ni
114. Iron loses its magnetic property at
(1043 K / 7700 C)
(A) Melting point         
(B) Curie point       
(C) 1000°C      
(D) Boiling point
115. Bell metal is an alloy of
(A) Cu + Sn       
(B) Cu + Zn        
(C) Cu + Ni       
(D) Cu + Mn
116. Which element has the greatest ductility property ?
(most ductile metal – platinum, malleable metal – gold)
(A) Cu      
(B) Ag        
(C) Au       
(D) Pt
117. Aluminum is extracted from bauxite by
(A) Bayer’s process       
(B) Downs process       
(C) Solvay process       
(D) Oswald process
118. The main radioactive element of pitch blende ore is
(A) Ra        
(B) Th        
(C) U      
(D) Po
119. The maximum consumption of refractories involves in
(A) Glass Industries       
(B) Iron and Steel Plants       
(C) Cement Plants      
(D) Petroleum Industries
120. The most common element in the universe is
(A) Fe       
(B) Ca        
(C) Al       
(D) Si   (28%)
121. The process of zone refining is used for ultra-purification of
(A) Silicon       
(B) Germanium       
(C) Gallium       
(D) All of the above
122. The base composition of whiteware body contains
(A) Clay, Quartz and Talc
(B) Quartz, Clay and Feldspar
(C) Talc, Bauxite and Wollastonite
(D) Clay, Gypsum and Feldsper
123. Which of the following metals do not form amalgam ?
(A) Iron        
(B) Sodium       
(C) Zinc      
(D) Magnesium
124. Jam-jelly can be preserved by adding small percentage of
(A) HCHO       
(B) EDTA       
(C) sodium benzoate      
125. Reverse of swelling of gel is known as
(A) Syneresis      
(B) Intestine       
(C) Adrenal gland       
(D) Blood
151. Which one of the following is not peroxide ?
(A) BaO2       
(B) Na2O2        
(C) H2O2        
(D) MnO2
152. Atomic packing density in FCC lattice is
(A) 0.47      
(B) 0.68       
(C) 0.74       
(D) 1.0
155. 44 g of CO2 occupies how many litres of CO2 at STP ?
(A) 2.4 L
(B) 2.24 L
(C) 44 L
(D) 22.4 L
159. The contact angle of Hg on glass
(A) = 90°      
(B) >90°    (138°)  
(C) <90°      
(D) None of the above
160. Forward chemical reactions happened only if
(A) ΔG = 0       
(B) ΔG > 0      
(C) ΔG < 0     
(D) None of the above
163. Diamond has the Mohs’ scale hardness number of
(A) 5       
(B) 7      
(C) 10     
(D) 9
164. Bakelite is the product of
(A) addition polymerization
(B) condensation polymerization
(C) co-polymerization
(D) None of the above
165. High polymerization of ethylene is done by using
(A) Zeolite catalyst      
(B) V2O5 catalyst       
(C) Zeiglar-Natta catalyst      
(D) Pt-Mo catalyst
166. The isotope used for cancer therapy
(P-32, Na-24, Sr-89, Cs-137, Sm-153, Ir-192, Ac-225)
(A) I80      
(B) Co60      
(C) C14     
(D) Ra223
167. Chemical used as insecticide is
(A)  γ-BHC       
(B) Methyl salicylate      
(C) Iodoform      
168. Number of unpaired electrons present in Cu2+.
(A) 3      
(B) 5       
(C) 2      
(D) 1
169. Which one of these is not a transitional metal ?
(A) Ti      
(B) Cr      
(C) Ni       
(D) Zn
171. Diazo-coupling reaction between diazonium salt and naphthol produces
(A) Green dye      
(B) Yellow dye       
(C) Red dye       
(D) Blue dye
172. Chemical formula of Grignard reagent is
(A) R-Mg-X      
(B) R-Ca-X       
(C) R-Sr-X       
(D) None of the above
176. The structure of α-alumina is
(A) Trigonal      
(B) Orthorhombic       
(C) Hexagonal       
(D) Cubic
192. The isotope used as fuel in nuclear power plant is
(A) U235      
(B) U238      
(C) U233      
(D) U239
178. Which of the following behaves as chemically most active non-metal ?
(A) F2     (Fluorine)
(B) He       
(C) N2       
(D) O2
179. A mixture of carbon monoxide and hydrogen is called
(A) Natural gas       
(B) Water gas        
(C) Producer gas       
(D) None of the above
180. Which fuel has the maximum calorific value ?
(Hydrogen highest – 150 KJ/g)
(A) Charcoal      
(B) Kerosene       
(C) Wood        
(D) LPG      (50 KJ/g)
181. The hydrolysis of cane sugar is catalyzed by
(A) H+      
(B) Enzymes        
(C) Mineral acid       
(D) All of the above
182. The catalyst used in the hydrogenation of oils is
(A) V2O5       
(B) Ni       
(C) Fe       
(D) Pt
183. Hydrochloric acid is also known is
(A) Chloric acid        
(B) Muriatic acid       
(C) Galic acid      
(D) Picric acid
184. Which one of the following element is essential for the construction of nuclear reactors ?
(A) Tungsten       
(B) Platinum        
(C) Cobalt       
(D) Zirconium
194. Martensitic steel has following crystal structure
(body-centered tetragonal crystal structure)
(A) BCC      
(B) FCC       
(C) BCT   


WBCS Main Question Paper – 2016

28. A gas is enclosed in a container which is then placed on a fast moving train. The temperature of the gas –
(A) falls       
(B) rises       
(C) remains unchanged      
(D) becomes unsteady
47. In nuclear reaction, there is conservation of-
(A) energy only       
(B) momentum only        
(C) mass, energy and momentum       
(D) mass only
49. Particles which can be added to the nucleus of atom without changing its chemical properties are
(A) electron        
(B) protons        
(C) neutrons        
(D) α-particles
69. The number of unpaired electrons in Mn2+ is –
(A) 1       
(B) 3        
(C) 4         
(D) 5
78. A radioactive decay process has a half-life of 4 yr. The amount of the reactant remaining after 12 years is
(A) 10%         
(B) 12.5%       
(C) 25%       
(D) 87.5%
91. Radioactive substance used in dating geological object is –
(A) C – 12        
(B) C – 11        
(C) C – 14       
(D) None of the above
103. The patient is asked to drink barium sulphate (BaSO4) for examining the stomach by X-rays because X-rays are
(A) less absorbed by heavy atoms
(B) more absorbed by heavy atoms
(C) reflected by heavy atoms
(D) refracted by heavy atoms
118. Which one of the following is not radioactive ?
(A) Astatine      
(B) Francium       
(C) Tritium        
(D) Zirconium

WBCS Main Question Paper – 2015

13.  Which of the following is natural polymer ?
(condensation polymer)
(A) Terylene      
(B) Orion       
(C) Starch      
(D) Dacron

15.  Marsh gas is
(CH4 + H2S + CO2)
(A) Methane       
(B) Ethane        
(C) Ethylene        
(D) None of the above
16.  In the metallurgy of iron, the material obtained from bottom of the blast furnace is
(A) Slag        
(B) Pig iron        
(C) Cast iron        
(D) Wrought iron
17.  The main ore of aluminum is
(A) Bauxite       
(B) Alumina       
(C) Potash-alum       
(D) Cryolite
18.  Which one is the unit of radio activity ?
(A) Curie       
(B) Tasla        
(C) Henry       
(D) Uranium
19.  When a lead storage cell is charged
(A) Sulphuric Acid is consumed         
(B) Sulphuric Acid is formed
(C) Lead sulphate is formed         
(D) Lead is consumed
20.  The temperature above which a real gas cannot be liquefied is known as
(A) Critical temperature        
(B) Boyle temperature 
(C) Inversion temperature     
(D) None of the above
22. Carnalite on electrolysis gives
A) Ca & Cl2
B) Na & CO2
C) Al & Cl2
D) Mg & Cl2
25. Which one is correct sequence in increasing order of molecular weights of the hydrocarbons?
(A) Methane, ethane, propane and butane
(B) Propane, butane, ethane and methane
(C) Butane, ethane, propane and methane
(D) Butane, propane, ethane and methane
26. Which one of the following is known as RDX?
(Royal Demolition eXplosive)
(A) Cyanohydrin
(B) Dextran
(C) Cyclohexane
(D) Cyclonite
29. Which one among the following is called Philosopher’s wool?
(A) Zinc Bromide
(B) Zinc Nitrate
(C) Zinc Oxide
(D) Zinc Chloride


31. Which one of the following does not contain silver?
(German silver – alloy of nickel, zinc & copper)
(A) Horn silver
(B) German silver    
(C) Ruby silver
(D) Lunar Caustic
33. Which one of the following is also called a stranger gas?
(A) Argon
(B) Neon
(C) Xenon
(D) Nitrous oxide
34. Which one of the following is used as an explosive?
(A) Phosphorus trichloride
(B) Mercuric oxide
(C) Graphite
(D) Nitroglycerine
35. Which one of the following sets of elements was primarily responsible for the origin of life on the Earth?
(A) Hydrogen, Oxygen, Sodium
(B) Carbon, Hydrogen, Nitrogen
(C) Oxygen, calcium, Phosphorus
(D) Carbon, Hydrogen, Potassium
42. D.D.T was invented by
(A) Paul Muller
(B) La Mark
(C) Pavlov
(D) Darwin
91. The total of a given mass of a gas at a given temperature depends on
(A) Pressure
(B) Volume
(C) Density
(D) Temperature
95. In a nuclear reactor the chain reaction is controlled by introducing
(A) Iron rods
(B) Cadmium rods
(C) Graphite rods
(D) Platinum rods
99. When water is heated from 0°C to 10°C. Its Volume
(A) Increases
(B) Decreases
(C) Does not change
(D) First decreases then increases
185. Which of the following is a good nuclear fuel?
(U-233, U-235 & P-239)
(A) Uranium-238
(B) Neptunium-239
(C) Plutonium-239
(D) Thorium-236
189. Most glass contain about 71 % by weight of
(A) Silicon dioxide
(B) Carbon dioxide
(C) Sulphur dioxide
(D) Calcium carbonate
191. Gunpowder consists of a mixture of
(A) sand and TNT
(B) Sulphur, Sand and charcoal
(C) Nitrate, Sulphur and Charcoal
(D) TNT and charcoal

WBCS Main Question Paper – 2014

6.  The reaction that takes place inside the Sun to power it is
(A) Fission        
(B) Fusion       
(C) Oxidation       
(D) Decay
12.  Naphthalene has the formula
(A) C6H6        
(B) C10H8      
(C) C12H10      
(D) C12H12
15.  The following substance is not an oxidizing agent
(A) Ozone      
(B) Chloride        
(C) Potassium       
(D) Fluorine
20.  The most electro-negative among the elements sodium, potassium, oxygen and fluorine is
(A) sodium       
(B) potassium       
(C) oxygen       
(D) fluorine
21.  The technique of barium X-ray utilizes the following property of barium sulphate
(A) It is opaque to X-rays      
(B) It is radioactive
(C) It is transparent to X-rays       
(D) It is easily absorbed by tissues
30.  The basic molecule binds with other molecules to form a polymer is called
(A) macromolecule       
(B) monomolecule        
(C) monomer       
(D) monolith
36.  The half-life period of an isotope is 2 hours. After 6 hours the fraction of the initial quantity of the isotope left behind will be
(A) 1/6       
(B) 1/8        
(C) 1/12      
(D) 1/16
39.  Epoxy resins are used as
(A) detergents       
(B) insecticides        
(C) adhesives      
(D) moth repellents
86.  Which of the following uranium isotopes is mostly used in nuclear reactors and nuclear weapons ?
(A) Uranium – 232       
(B) Uranium – 234        
(C) Uranium – 235      
(D) Uranium – 238

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