CHEMICAL AND IONIC EQUILIBRIA MCQs

By: Prof. Dr. Fazal Rehman | Last updated: May 23, 2025

1. : Which statement is not true regarding Lewis acids and bases?
(A) Lewis base must contain an atom having less than an octet of electron
(B) Substances which donate a pair of electrons are called Lewis bases
(C) All Lewis bases are also Bronsted bases
(D) NH3 and H2O both behave as Lewis bases

2. : At equilibrium the free energy change (ΔF) for a reaction is
(A) Zero
(B) Minimum
(C) Maximum
(D) Infinite

3. : Which properties of a system does not change in a state of equilibrium?
(A) Concentration
(B) Density
(C) Pressure
(D) All of A, B, and C

4. : In the equilibrium reaction N2 + 3H2 ⇄ 2NH3 + 22.9kcal, the equilibrium shifts to the forward direction when ________ .
(A) Increasing the P as well as T
(B) Decreasing the P as well as T
(C) Increasing the P and decreasing the T
(D) Decreasing the P and increasing the T

5. : According to Le-Chatlier’s principle, the formation of NO2 at equilibrium in the reaction should be helped by
2NO + O2 ⇄ 2NO2 + heat
(A) Low T, high P
(B) Low T and low P
(C) High T and high P

6. : Formation of SO3 takes place according to the reaction
2SO2 + O2 ⇄ 2SO3 ΔH = -45.2 kcal. Which factors will help the formation of SO3?
(A) Increase of T
(B) Removal of O2
(C) Increase of P

7. : For which equilibrium does decrease in pressure not help the forward reaction?
(A) CaCO3 ⇄ CaO + CO2
(B) 2NH3 ⇄ N2 + 3H2
(C) NH4Cl ⇄ NH3 + HCl
(D) CO + 2H2 ⇄ CH3OH

8. : Four moles of A are mixed with four moles of B when 2 moles of C are formed at equilibrium, according to the reaction A + B ⇄ C + D. What is the value of the equilibrium constant?
(A) 8
(B) 1
(C) 1/4
(D) 2/2

9. : When 3 moles of ethyl alcohol are mixed with 3 mole of acetic acid, 2 moles of ester are formed at equilibrium according to the equation:
CH3COOH + C2H5OH ⇄ CH3COOC2H5 + H2O
What is the value of the equilibrium constant?
(A) 4
(B) 4/9

10. : In the reaction HCN + H2O ⇄ H3O+ + CN−, the conjugate acid-base pair is
(A) HCN, H3O+
(B) HCN, CN−
(C) CN−, H3O+
(D) H2O, CN−

11. : According to Arrhenius theory, an acid is defined as a substance which
(A) Furnishes H2O+ ion in water
(B) Donates H+ ion in ammonia
(C) Contains Cl− ions
(D) Accepts an electron pair

12. : Which can act both as a Bronsted acid and a Bronsted base?
(A) Na2CO3
(B) HCO3−
(C) OH−
(D) NH3

13. : Which is not a Lewis base?
(A) CN−
(B) NH3
(C) ROH
(D) AlCl3

14. : Which statement is not related with chemical equilibrium?
(A) The chemical equilibrium is static in nature
(B) The equilibrium can be approached from either direction
(C) The chemical equilibrium is dynamic in nature
(D) The properties of the system become constant

15. : HS− is a conjugate base of
(A) S2−
(B) H2SO4
(C) H2SO3
(D) H2S

16. : Which acid-base reaction is according to Lewis classification?
(A) H+ + OH− ⇄ H2O
(B) HCN + H2O ⇄ H3O+ + CN−
(C) H2O + H2O ⇄ H3O+ + OH−
(D) (CH3)3N + BF3 ⇄ (CH3)3N:BF3

17. : The sum of pH and pOH in aqueous solution is equal to
(A) 14
(B) 7
(C) pKw
(D) Zero

18. : The value of Kw at 25°C is
(A) 14
(B) 1.4
(C) 0.14
(D) 1×10⁻¹⁴

19. : Which solution has pH = 11?
(A) 1×10⁻³ M NaOH
(B) 1×10⁻¹¹ M HCl
(C) 1×10⁻¹¹ M NaOH
(D) 1×10³ M NaOH

20. : What is the pKa of an acid having ionization constant 1×10⁻⁵?
(A) -3
(B) -9
(C) 9
(D) 5

21. : Which will have the higher pH?
(A) 0.1 N NaOH
(B) 0.1 N CH₃COOH
(C) 0.1 N HCl
(D) 0.01 N HCl

22. : The pink colour of phenolphthalein in basic medium is due to the
(A) Cationic form
(B) OH⁻ ions of the base
(C) Neutral form
(D) Anionic form

23. : A buffer solution can be prepared from
(A) CH₃COOH and CH₃COONa
(B) CH₃COOH and HCl
(C) CH₃COOH and NaOH
(D) CH₃COONa and HCl

24. : The true order of increasing acid strength is
(A) HNO₄ < H₂N₂O₂ < HNO₂
(B) H₂N₂O₂ < HNO₃ < HNO₂
(C) HNO₂ < HNO₃ < H₂N₂O₂
(D) H₂N₂O₂ < HNO₂ < HNO₃

25. : The true order of acidic strength is
(A) HF < HCl < HBr < HI
(B) HI < HBr < HCl < HF
(C) HI < HBr < HF < HCl
(D) HF < HCl < HI < HBr

26. : What is the true order of acid strength?
27. : Which species is a stronger acid than formic acid (HCOOH) in aqueous solution?
(A) H₂SO₄
(B) NH₄⁺
(C) CH₃COOH
(D) H₄P₂O₇

28. : The degree of dissociation of weak acid increases with
(A) Decreasing concentration
(B) Increasing pressure
(C) Increasing concentration
(D) Decreasing pressure

29. : A 2 M solution of H₂SO₄ would have how many moles of H⁺ ion in one liter?
(A) 1.0
(B) 4.0
(C) 7.0
(D) 2.0

30. : Which hypothetical reaction is helped by increase of temperature and pressure?
(A) 2A + B ⇄ C + D ΔH = +ve
(B) A + 2B ⇄ 2C + D ΔH = +ve
(C) A + B ⇄ C + D ΔH = -ve
(D) 2A + 2B ⇄ 2C + 2D ΔH = -ve

31. : What is the pH of a neutral solution at 100°C when Kw = 1.0 × 10⁻¹²?
(A) 6
(B) 4
(C) 0
(D) 2

32. : The pKa of acetic acid is 4.74, which implies that
(A) pH of 1N solution is 4.74
(B) At pH 4.74, the dissociation of acetic acid is minimum
(C) At pH 4.74, the dissociation of acetic acid is maximum
(D) At pH 4.74, half of the acetic acid molecules are dissociated in the solution

33. : Which is a buffer solution?
(A) CH₃COOH + CH₃COONa
(B) CH₃COOH + HCl
(C) CH₃COOH + NaOH
(D) CH₃COOH + NH₄OH

34. : Which is not a buffer?
(A) H₂CO₃/HCO₃⁻
(B) NH₄OH/CH₃COOH
(C) CH₃COOH/CH₃COONa
(D) NH₄Cl/NH₄Cl

35. : Which parameter of a chemical reaction will change with the use of a catalyst?
(A) K, the rate constant
(B) ΔS, change in entropy
(C) ΔE, change in internal energy
(D) ΔP, change in free energy

36. : What is the approximate pH of human blood?
(A) 7.5
(B) 6.2
(C) 7.8
(D) 7.2

37. : Azeotropic mixture can be separated by which of the following?
(A) Vacuum distillation
(B) Fractional distillation
(C) Simple distillation
(D) Destructive distillation

38. : Which has highest pH?
(A) 0.1 M HCl
(B) 0.2 M HCl
(C) 0.1 M HNO₃
(D) 0.1 M NaOH

39. : If 20 ml of 0.5 N salt solution is diluted to one litre, what is the new concentration?
(A) 1 N
(B) 0.001 N
(C) 0.01 N
(D) 10 N

40. : The pH of milk is
(A) 5.5
(B) 8.5
(C) 7.5
(D) 6.5

41. : What is the pH of soft drink?
(A) 2
(B) 6
(C) 5
(D) 3

42. : What is the sum of [H⁺] and [OH⁻] in pure water?
(A) 7
(B) 14
(C) 20
(D) 12

43. : Which affect the Kc value?
(A) Catalyst
(B) Pressure
(C) Temperature
(D) All of A, B, and C

44. : What is the pH of 0.001 M HCl in water?
(A) 5
(B) 3
(C) 2
(D) 4

45. : What is the pH of 0.001 M NaOH?
(A) 14
(B) 11
(C) 13
(D) 12

46. : What is the molarity of pure water?
(A) 7 M
(B) 18 M
(C) 55.5 M
(D) 14 M

47. : The precipitation occurs if the ionic concentration is:
(A) More than Ksp
(B) Less than Ksp
(C) Equal to Ksp
(D) None of A, B, and C