JEE Chemistry Equilibrium MCQs Set B

Question:  Which one of the following information can be obtained on the basis of Le Chatelier principle?

• a) Shift in equilibrium position on changing value of a constraint
• b) Equilibrium constant of a chemical reaction
• c) Entropy change in a reaction
• d) Dissociation constant of a weak acid

Answer: Shift in equilibrium position on changing value of a constraint

Question:

• a) Low temperature, high pressure and catalyst
• b) Low temperature, low pressure and catalyst
• c) High temperature, low pressure and catalyst
• d) High temperature, high pressure and catalyst

Answer: Low temperature, high pressure and catalyst

Question: Which of the following reaction will be favoured at low pressure ?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  The equilibrium which remains unaffected by pressure

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Suitable conditions for melting of ice

• a) high temperature and high pressure
• b) high temperature and low pressure
• c) low temperature and low pressure
• d) low temperature and high pressure

Answer: high temperature and high pressure

Question: In which of the following reactions, the equilibrium remains unaffected on addition of small amount of argon at constant volume?

• a) The equilibrium will remain unaffected in all the three cases.
• b)

  

• c)

  

• d)

  

Answer: The equilibrium will remain unaffected in all the three cases.

Question:  Le-Chatelier principle is not applicable to

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: In an equilibrium reaction if temperature increases

• a) any of the above
• b) no effect
• c) equilibrium constant decreases
• d) equilibrium constant increases

Answer: any of the above

Question:

• a) low pressure, low temperature and high pressure, low temperature
• b) low pressure, high temperature and high pressure, high temperature
• c) high pressure, low temperature and low pressure, high temperature
• d) high pressure, high temperature and low pressure, low temperature

Answer: low pressure, low temperature and high pressure, low temperature

Question:  What happens when an inert gas is added to an equilibrium keeping volume unchanged?

• a) More product will form
• b) Less product will form
• c) More reactant will form
• d) Equilibrium will remain unchanged

Answer: More product will form

Question: In a vessel N₂, H₂ and NH₃ are at equilibrium. Some helium gas is introduced into the vessel so that total pressure increases while temperature and volume remain constant. According to Le Chatelier’s principle, the dissociation of NH₃

• a) remains unchanged
• b) increases
• c) decreases
• d) equilibrium is disturbed

Answer: remains unchanged

Question:  Effect of a catalyst on a equilibrium reaction

(i) A catalyst increases the rate of the chemical reaction by making available a new low energy pathway for the conversion of reactants to products.
(ii) It increases the rate of forward and reverse reactions that pass through the same transition state and does not affect equilibrium.
(iii) It lowers the activation energy for the forward and reverse reactions by exactly the same amount.

Which of the above statement(s) is/are correct ?

• a) (i), (ii) and (iii)
• b) Only (i) 
• c) (i) and (ii)
• d) (ii) and (iii)

Answer: (i), (ii) and (iii)

More Questions....................................

Question:  Which of the following is/are electrolytes?

(i) Sugar solution (ii) Sodium chloride
(iii) Acetic acid      (iv) Starch solution

• a) (ii) and (iii)
• b) (i) and (iv)
• c) (ii) and (iv)
• d) (i) and (iii)

Answer: (ii) and (iii)

Question: The geometry of hydronium ion is

• a) trigonal pyramidal
• b) tetrahedral
• c) linear
• d) trigonal planer

Answer: trigonal pyramidal

Question: Which of the following statements are correct regarding Arrhenius theory of acid and base?

• a) Both
• b) This theory could not explain the basicity of substances like ammonia which do not possess a hydroxyl group
• c) This theory was applicable to all solutions
• d) This theory was applicable to only aqueous solutions

Answer: Both

Question: Would gaseous HCl be considered as an Arrhenius acid ?

• a) No
• b) Not known
• c) Gaseous HCl does not exist
• d) Yes

Answer: No

Question:  A base, as defined by Bronsted theory, is a substance which can

• a) accept protons
• b) gain a pair of electrons
• c) donate protons
• d) lose a pair of electrons

Answer: accept protons

Question: BF₃ is an acid according to

• a) Lewis Concept
• b) Arrhenius concept
• c) Bronsted-Lowry concept
• d) None of these

Answer: Lewis Concept

Question: Which of the following can act as both Bronsted acid and Bronsted base?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) NH₃
• b) NH
• c) NH₂
• d) None of these

Answer: NH₃

Question: Among boron trifluoride, stannic chloride and stannous chloride, Lewis acid is represented by

• a) boron trifluoride and stannous chloride
• b) only boron trifluoride
• c) boron trifluoride and stannic chloride
• d) only stannic chloride

Answer: boron trifluoride and stannous chloride

Question: Which of the following molecules acts as a Lewis acid ?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which one of the following molecular hydrides acts as a Lewis acid?

• a) B₂H₆
• b) NH₃
• c) H₂O
• d) CH₄

Answer: B₂H₆

Question: Which of these is least likely to act as Lewis base?

• a) BF₃
• b) CO
• c) F^–
• d) PF₃

Answer: BF₃

Question: Which one of the following is the correct statement ?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Water is well known amphoprotic solvent. In which chemical reaction water is behaving as a base?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: An acid/ base dissociation equilibrium is dynamic involving a transfer of proton in forward and reverse directions. Now, with passage of time in which direction equilibrium is favoured ?

• a) in the direction of formation of weaker base and weaker acid
• b) in the direction of formation of weaker base and stronger acid
• c) in the direction of formation of stronger base and weaker acid
• d) in the direction of stronger base and stronger acid

Answer: in the direction of formation of weaker base and weaker acid

Question:

• a) (ii) only
• b) (iii) only
• c) (i) and (ii)
• d) (i) only

Answer: (ii) only

Question: The value of the ionic product of water

• a) depends on temperature
• b) changes by adding acid or alkali
• c) always remains constant
• d) depends on volume of water

Answer: depends on temperature

Question: A base when dissolved in water yields a solution with a hydroxyl ion concentration of 0.05 mol litre^–1. The solution is

• a) basic
• b) neutral
• c) acidic
• d) None of these

Answer: basic

Question:  pH scale was introduced by

• a) Sorensen
• b) Lowry
• c) Lewis
• d) Arrhenius

Answer: Sorensen

Question: pH of solution is defined by expression

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The pH of a 10^–3 M HCl solution at 25°C if it is diluted 1000 times, will be –

• a) 5.98
• b) 6.02
• c) zero
• d) 3

Answer: 5.98

Question: How many litres of water must be added to 1 litre an aqueous solution of HCl with a pH of 1 to create an aqueous solution with pH of 2 ?

• a) 9.0 L
• b) 0.9 L
• c) 0.1 L
• d) 2.0 L

Answer: 9.0 L

Question: What is the approximate pH of a 1 × 10^–3 M NaOH solution?

• a) 11
• b) 1 × 10^–11
• c) 3
• d) 7

Answer: 11

Question: Calculate the pOH of a solution at 25°C that contains 1× 10^{– 10} M of hydronium ions, i.e. H₃O⁺.

• a) 4.000
• b) 1.000
• c) 7.000
• d) 9.0000

Answer: 4.000

Question: The pH value of a 10 M solution of HCl is

• a) less than 0
• b) equal to 1
• c) equal to 0
• d) equal to 2

Answer: less than 0

Question:  What is the H⁺ ion concentration of a solution prepared by dissolving 4 g of NaOH (Atomic weight of Na = 23 amu) in 1000 ml?

• a) 10^–13 M
• b) 10^–4 M
• c) 10^–10 M
• d) 10^–1 M

Answer: 10^–13 M

Question: Calculate the pOH of a solution at 25°C that contains 1× 10^{– 10} M of hydronium ions, i.e. H₃O⁺.

• a) 4.000
• b) 1.000
• c) 9.0000
• d) 7.000

Answer: 4.000

Question: The pH of 0.005 molar solution of H₂SO₄ is approximately:

• a) 2
• b) 0.010
• c) 1
• d) 0.005

Answer:  2

Question: Which solution has pH equal to 10 ?

• a) 10^–4 M KOH
• b) 10^–10 M HCl
• c) 10^–10 M KOH
• d) 10^–4 M HCl

Answer: 10^–4 M KOH

Question:  Which of the following has highest pH ?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A weak acid, HA, has a K_a of 1.00 × 10^–5. If 0.100 mole of this acid dissolved in one litre of water, the percentage of acid dissociated at equilbrium is closest to

• a) 1.00%
• b) 0.100%
• c) 99.9%
• d) 99.0%

Answer: 1.00%

Question:  A monobasic weak acid solution has a molarity of 0.005 and pH of 5. What is the percentage ionization in this solution?

• a) 0.2
• b) 0.25
• c) 2.0
• d) 0.5

Answer: 0.2

Question: Calculate the pH of a solution obtained by diluting 1 mL of 0.10 M weak monoacidic base to 100 mL at constant temperature if K_b of the base is 1 × 10^–5 ?

• a) 10
• b) 8
• c) 9
• d) 11

Answer: 10

Question:

• a) formic acid > acetic acid > hypochlorous acid
• b) formic acid > hypochlorous acid > acetic acid
• c) hypochlorous acid > acetic acid > formic acid
• d) acetic acid > hypochlorous acid > formic acid

Answer: formic acid > acetic acid > hypochlorous acid

Question: The first and second dissociation constants of an acid H₂A are 1.0 × 10^–5 and 5.0 × 10^–10 respectively. The overall dissociation constant of the acid will be

• a) 5.0 × 10^–15.
• b) 5.0 × 10^–5
• c) 0.2 × 10⁵
• d) 5.0 × 10¹⁵

Answer:  5.0 × 10^–15.

Question: Equimolar solutions of HF, HCOOH and HCN at 298 K have the values of K_a as 6.8 × 10^–4 and 4.8 × 10^–9 respectively. What is the observed trend of dissociation constants in successive stages ?

• a) HF > HCOOH > HCN
• b) HCOOH > HCN > HF
• c) HF > HCN > HCOOH
• d) HCN > HF > HCOOH

Answer: HF > HCOOH > HCN

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Which of the following pK_a value represents the strongest acid ?

• a) 10^–8
• b) 10^–2
• c) 10^–4
• d) 10^–5

Answer: 10^–8

Question: The dissociation constant of two acids HA₁ and HA₂ are 3.14 × 10_{– 4} and 1.96 × 10_{– 5} respectively. The relative strength of the acids will be approximately

• a) 4 : 1
• b) 16 : 1
• c) 1 : 4
• d) 1 : 16

Answer: 4 : 1

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: At 298K a 0.1 M CH₃COOH solution is 1.34% ionized. The ionization constant K_a for acetic acid will be

• a) 1.82 × 10^{– 5}
• b) 0.182 × 10 ^–5
• c) 18.2 × 10 ^–5
• d) None of these

Answer: 1.82 × 10^{– 5}

Question: For dibasic acid correct order is

• a)

  

• b)

  

• c)

  

• d) not certain

Answer:

Question: For a polybasic acid, the dissociation constants have a different values for each step, e.g.,

What is the observed trend of dissociation constants in successive stages ?

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Cationic hydrolysis gives the following solution

• a) acidic
• b) basic
• c) amphoteric
• d) neutral

Answer: acidic

Question: In qualitative analysis, in III group NH₄Cl is added before NH₄OH because

• a) to reduce the concentration of OH^– ions
• b) to increase concentration of OH^– ions
• c) to increase concentration of Cl^– ions
• d) None of these

Answer:  to reduce the concentration of OH^– ions

Question: The solubility of AgI in NaI solution is less than that in pure water because

• a) of common ion effect
• b) AgI forms complex with NaI
• c) solubility product to AgI is less than that of NaI
• d) None of these

Answer: of common ion effect

Question: When sodium acetate is added to an aqueous solution of acetic acid

• a) The pH of the solution increases
• b) The pH of the solution decreases
• c) An acid salt is produced

Answer: The pH of the solution increases