West Bengal Joint Entrance Examinations Board (WBJEEM) chemistry 50 questions and answers.

Ques. The ratio of the amount of H₂S needed to precipitate all the metal ions from 100 c.c. of 1 M AgNO₃ and 100 c.c. of 1 M CuSO₄ will be
(a) 1 : 1
(b) 2 : 1
(c) 2 : 1
(d) Indefinite
Ans. (c)

Ques. When 10 gm of Na₂SO₄, xH₂O is heated to dryness 5.035 gm water vapour is produced, therefore the value of x is
(a) 10
(b) 7
(c) 6
(d) 8
Ans. (d)

Ques. HI was heated in a sealed tube at 400°C till the equilibrium was stablished. HI was found to be 22% decomposed. The equilibrium constant for dissociation HI D ½ H₂ + ½ I₂ is
(a) 0.282
(b) 0.0796
(c) 0.0199
(d) 1.99
Ans. (c)

Ques. One mole of mixture of N₂, NO₂ and N₂O₄ has a mean molar mass of 55.4. On heating to a temperature at which all the N₂O₄ may be presumed to have dissociated : N₂O₄ D 2NO₂, the mean molar mass tends to the lower value of 39.6. What is the mole ratio of N₂ : NO₂ : N₂O₄ in the original mixture
(a) 0.5 : 0.1 : 0.4
(b) 0.6 : 0.1 : 0.3
(c) 0.5 : 0.2 : 0.3
(d) 0.6 : 0.2 : 0.2
Ans. (a)

Ques. X is a 100 ml Solution of HNO₃ whose dilution is 1000. Y is the second 100 ml of solution of HNO₃ whose concentration is C. The pH becomes 1 on mixing X and Y in a beaker, then the value of C will be
(a) 0.199 N
(b) 0.10 N
(c) 0.30 N
(d) 0.50 N
Ans. (a)

Ques. What is the pH value of 1 N CH₃COONH₄
(a) ½ pK_w
(b) pK_w
(c) 2 pK_w
(d) 12 pK_w
Ans. (a)

Ques. A cylinder of compressed gas bears no label is supposed to contain either ethylene (C₂H₄) or propylene (C₃H₆). Combustion of the gaseous sample shows that 12mL of gas required 54 mL of oxygen for complete combustion. This indicates that the gas is
(a) Only ethylene
(b) Only propylene
(c)  mixture of two gases
(d) Some unknown mixture of two gases
Ans. (b)

Ques. At the top of the mountain the thermometer reads 0°C and the barometer reads 710 mm Hg. At the bottom of the mountain the temperature is 30°C and pressure is 760 mm Hg. Density of air at the top with that at the bottom is
(a) 1 : 1
(b) 1.04 : 1
(c) 1 : 1.04
(d) 1.15
Ans. (b)

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Ques. A solution of 500 ml of 0.2 M KOH and 500 ml of 0.2M HCl is mixed and stirred; the rise in temperature is T₁. The experiment is repeated using 250 ml each of solution, the temperature raised is T₂. Which of the following is true
(a) T₁ = T₂
(b) T₁ = 2T₂
(c) T₁ = 4T₂
(d) T₂ = 9T₁
Ans. (a)

Ques. The indicator used in the titration of KMnO₄ against FeSO₄ is
(a) Phenolphthalein
(b) K₃Fe(CN)₆
(c) None
(d) Methyl orange
Ans. (c)

Ques. 2 gm of a metal when treated with air gave 2.8 gm of its oxide. The molecular formula of its chloride is MCl₂. The atomic weight of the metal is
(a) 20
(b) 40
(c) 60
(d) 80
Ans. (b)

Ques. Oxidation number of phosphorus in Ba(H₂PO₂)₂ is
(a) +3
(b) +2
(c) +1
(d) –1
Ans. (c)

Ques. How many primary, secondary, tertiary and quaternary carbons are present in the following hydrocarbon CH₃ – CH(CH₃) – C(CH₃)₂ – CH₂ – CH(CH₃) – CH₂ – CH₃

Ans. (a)

Ques. Stability number of neutrons is present in which of the following elements
(a) ₁₃Al²⁷
(b) ₈₃Bi²⁰⁹
(c) ₉₂U²³⁸
(d) ₂₆Fe⁵⁶
Ans. (b)

Ques. Wavelength of gamma rays is
(a) 10^–7 m
(b) 10^–10 m
(c) 10^–8 m
(d) 10^–12 m
Ans. (d)

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Ques. Which of the following statements is false
(a) Catalyst starts the reaction
(b) Catalyst remains unchanged in amount and constitution after the reaction
(c) Catalyst does not shift the equilibrium in a reversible reaction
(d) None of these
Ans. (a)

Ques. The catalyst used in the manufacture of ether from alcohol is
(a) Al₂O₃
(b) CrO₃
(c) MnO
(d) None of these
Ans. (a)

Ques. In the Fischer-Tropsch synthesis of petrol….. and ….. are used as the raw materials
(a) H₂ ; CO
(b) CH₄ ; H₂
(c) CH₄ ; CH₃OH
(d) CH₃ OH ; CO
Ans. (a)

Ques. According to Hardy-Schulze low, in order to coagulate a certain amount of a colloid, the amount of electrolyt used depends on
(a) Opposite charge on ion
(b) Size of ion
(c) Nature of ion
(d) Shape of ion
Ans. (a)

Ques. Oxidation number of S in H₂S₂O₇ is
(a) +4
(b) –6
(c) –5
(d) +6
Ans. (d)

Ques. A gas decolourises bromine water and on reacting with hydrogen bromide forms bromoethene and ethylidene bromide the gas is
(a) Propane
(b) Propene
(c) Ethene
(d) Ethyne
Ans. (d)

Ques. Size of a colloidal particle is
(a) 10 – 1000 Å
(b) 200-100 Å
(c) 20–50 Å
(d) 1–20 Å
Ans. (a)

Ques. Monomer of neoprene is
(a) Isoprene
(b) Chloroprene
(c) Vinyl chloride
(d) Vinyl acetylene
Ans. (b)

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Ques. Acelylene on polymerization gives
(a) Vinyl acetylene
(b) Cyclooctatetraene
(c) Benzene
(d) All of these
Ans. (d)

Ques. Which of the following sols is positively charged?
(a) As₂O₃
(b) Fe(OH)₃
(c) Au
(d) Starch
Ans. (b)

Ques. Which of the following compounds does not form a carbonyl compound on hydrolysis?
(a) (CH₃)₃CCHCl₂
(b) (CH₃)₃CCCl₃
(c) (CH₃)₂CCl₂
(d) (CH₃)₂CHCHCl₂
Ans. (b)

Ques. Which of the following types of reactions is not exhibited by diethyl ether
(a) Salt formation
(b) Neucleophilic substitution
(c) Free radical substitution
(d) Electrophilic substitution
Ans. (d)

Ques. Which of the following products is formed on the reaction of diethyl ether with chlorine in the presence of direct sunlight
(a) CCl₃ – CH₂ – O – CH₂ – CCl₃
(b) ClCH₂ – CH₂ – O – CH2 –CH₂Cl
(c) CCl₃ – C(Cl₂) – O – C(Cl₂) – CCl₃
(d) (CH₃ – CH – Cl)₂O
Ans. (c)

Ques. Which of the following acids does not form phenol when its sodium salt is dry distilled with soda lime?
(a) p-Hydroxybenzoic acid
(b) Salicylic acid
(c) m-Hydroxybenzoic acid
(d) Aspirin
Ans. (d)

Ques. The values of dissociation constants of some acids (at 25^oC) are as follows. Indicate which is the strongest acid in water
(a) 1.4 x 10^–2
(b) 1.6 x 10^–4
(c) 4.4 x 10^–10
(d) 4.3 x 10^–7
Ans. (a)

Ques. The 2N aqueous solution of H₂SO₄ contains
(a) 49 gm of H₂SO₄ per litre of solution
(b) 4.9 gm of H₂SO₄ per litre of solution
(c) 98 gm of H₂SO₄ per litre of solution
(d) 9.8 gm of H₂SO₄ per litre of solution
Ans. (c)

Ques: Which one of the following compounds when heated with KOH and a primary amine gives carbylamine test
(a) CHCl₃
(b) CH₃Cl
(c) CH₃OH
(d) CH₃CN
Ans: (a)

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Ques. The equivalent weight of phosphoric acid (H₃PO₄) in the reaction, NaOH + H₃PO₄ NaH₂PO₄ + H₂O is
(a) 25
(b) 49
(c) 59
(d) 98
Ans. (d)

Ques. From the given sets of quantum numbers the one that is inconsistent with the theory is
(a) n = 3; l = 2; m = –3; s = +1/2
(b) n = 4; l = 3; m = 3; s = +1/2
(c) n = 2; l = 1; m = 0; s = –1/2
(d) n = 4; l = 3; m = 2; s = +1/2
Ans. (a)

Ques. In which of the following reactions, there is no change in the valency
(a) 4KClO₃ 3KClO₄ + KCl
(b) SO₂ + 2H₂S 2H₂O + 3S
(c) BaO₂ + H_­2SO₄ BaSO₄ + H₂O₂
(d) 2BaO + O₂ 2BaO₂
Ans. (c)

Ques. The following graph illustrates

(a) Dalton’s law
(b) Charle’s law
(c) Boyle’s law
(d) Gay-Lussac’s law
Ans. (b)

Ques. One mole of SO₃ was placed in a litre reaction vessel at a certain temperature. The following equilibrium was established  2SO₃ ⇌ 2 SO₂ + O₂. At equilibrium 0.6 moles of SO₂ were formed. The equilibrium constant of the reaction will be
(a) 0.36
(b) 0.45
(c) 0.54
(d) 0.675
Ans. (d)

Ques. The ability of an ion to bring about coagulation of a given colloid depends upon
(a) Its size
(b) The magnitude of its charge only
(c) The sign of its charge
(d) Both the magnitude and the sign of its charge
Ans. (d)

Ques. Aluminium is a self–preserving metal, because
(a) It is not tarnished by air
(b) A thin film of basic carbonate on its surface
(c) A non-porous layer of oxide is formed on its surface
(d) It is not affected by salt water
Ans. (c)

Ques. There is a negative charge on As₂S₃ sol. Which of the following salts maximum capacity of precipitating it
(a) AlCl₃
(b) Na₃PO₄
(c) CaCl₂
(d) K₂SO₄
Ans. (a)

Ques. Coagulation power in which of the following is maximum
(a) Pb⁺²
(b) Pb⁺⁴
(c) Sr⁺²
(d) Na⁺
Ans. (b)

Ques. Which of the following statements is false
(a) Physical adsorption occurs due to van der Waals forces
(b) Chemical adsorption decreases at high temperature and low pressure
(c) For chemical adsorption, adsorption energy is generally more than that in physical adsorption
(d) All the above statements are true
Ans. (d)

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Ques. P₄ + 3NaOH + 3H₂O – – A + 3NaH₂PO₂ here, ‘A‘ is
(a) NH₃
(b) PH₃
(c) H₃PO₄
(d) H₃PO₃
Ans. (b)

Ques. The correct order of ionic radii of Y^3–, La³⁺, Eu³⁺ and Lu³⁺ is
(a) La³⁺3+ 3+ 3+
(b) Y^3–3+ 3+ 3+
(c) Lu³⁺ 3+ 3+ 3+
(d) Lu³⁺3+ 3+ 3+
(Atomic No. Y = 39, La = 57, Eu = 63, Lu = 71)
Ans. (c)

Ques. Credit for the ring structure of benzene goes to
(a) Wholer
(b) Faraday
(c) Kekule
(d) Baeyer
Ans. (c)

Ques. Gold number of which of the following is minimum
(a) Gelatine
(b) Starch
(c) Gum
(d) Equal for all of the above
Ans. (a)

Ques. Concentration of Ca⁺² is 40 mg/litre for hard water, then how many mg of Na₂CO₃ will be required to prepare soft water from 5 liters of hard water
(a) 530
(b) 5.3
(c) 1.06
(d) 10.6
Ans. (a)

Ques. Dimethyl ether and ethyl alcohol are
(a) Metamers
(b) Homologues
(c) Functional isomers
(d) Position isomers
Ans. (c)

Ques. When a beam of light is passed through a colloidal solution, then this beam of light?
(a) Gets diffracted
(b) Passes unchanged
(c) Shows a rainbow
(d) Gets dispersed
Ans. (d)

Ques. Nature of charge on the particles can be determined, by which of the following properties of a colloidal systems
(a) Electrophoriesis
(b) Dialysis
(c) Absorption
(d) Ultamicrofiltration
Ans. (a)

Ques. Which of the following is the reasons for the sky generally appearing blue?
(a) Deviation effect
(b) Conduction
(c) Reflection
(d) Dispersion
Ans. (d)

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