Chemical Equilibrium Questions and Answers with FREE PDF

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Chemical Equilibrium Questions and Answers with FREE PDF

1. At a particular temperature and atmospheric pressure, the solid and liquid phases of a pure substance can exist in equilibrium. Which of the following Does the term define this temperature?

(A) Normal melting point

(B) Equilibrium temperature

(C) Boiling point

(D) Freezing point

Answer: A, D

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

(A) H2 (g) + I2 (g) ⇌ 2HI (g)

(B) PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)

(C) N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

(D) The equilibrium will remain unaffected in all the three cases.

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

3. At 500 K, the equilibrium constant, 6Kc, for the following reaction is 5.

1/2 H2 (g) +1/2 I2 (g) HI (g) ——– What would be the equilibrium constant Kc for the reaction 2HI (g) H2 (g) + I2 (g)

(A) 0.04

(B) 0.4

(C) 25

(D) 2.5

Answer: 0.04

4. On increasing the pressure, in which direction will the gas-phase reaction proceed to re-establish equilibrium, is predicted by applying Le Chatelier’s principle. Consider the reaction.

N2 (g) + 3H2 (g) 2NH3 (g)

Which of the following is correct, if the total pressure at which the equilibrium is established, is increased without changing the temperature?

(A) K will remain the same

(B) K will decrease

(C) K will increase

(D) K will increase initially and decrease when pressure is very high

Answer: K will remain the same

5. PCl5, PCl3 and Cl2 are at equilibrium at 500K in a closed container and their concentrations are 0.8 × 10–3 mol L–1, 1.2 × 10–3 mol L–1 and 1.2 × 10–3 mol L–1 respectively. The value of Kc for the reaction PCl5 (g)  PCl3 (g) + Cl2 (g) will be

(A) 1.8 × 103 mol L–1

(B) 1.8 × 10–3

(C) 1.8 × 10–3 L mol–1

(D) 0.55 × 104

Answer: 1.8 × 10–3

6. Which of the following is not a general characteristic of equilibria involving physical processes?

(A) Equilibrium is possible only in a closed system at a given temperature.

(B) All measurable properties of the system remain constant.

(C) All the physical processes stop at equilibrium.

(D) The opposing processes occur at the same rate and there is dynamic but stable condition.

Answer: All the physical processes stop at equilibrium.

7. For the reaction H2(g) + I2(g) → 2HI (g), the standard free energy is ∆G > 0. The equilibrium constant (K ) would be __________.

(A) K = 0

(B) K > 1

(C) K = 1

(D) K < 1

Answer: K < 1

8. PCl5, PCl3 and Cl2 are at equilibrium at 500K in a closed container and their concentrations are 0.8 × 10–3 mol L–1, 1.2 × 10–3 mol L–1 and 1.2 × 10–3 mol L–1 respectively. The value of Kc for the reaction PCl5 (g) PCl3 (g) + Cl2 (g) will be

(A) 1.8 × 103 mol L–1

(B) 1.8 × 10–3

(C) 1.8 × 10–3 L mol–1

(D) 0.55 × 104

Answer: 1.8 × 10–3

9. Which of the following statements is incorrect?

(A) In equilibrium mixture of ice and water kept in perfectly insulated flask mass of ice and water does not change with time.

(B) The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.

(C) On addition of catalyst the equilibrium constant value is not affected.

(D) Equilibrium constant for a reaction with negative ΔH value decreases as the temperature increases.

Answer: The intensity of red colour increases when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.

10. In a reversible chemical reaction at equilibrium, if the concentration of any one of the reactants is doubled, then the equilibrium constant will

(A) Also be Doubled

(B) Be Halved

(C) Remain the Same

(D) Become One-Fourth

Answer: Remain the Same

11. On increasing the concentration of reactants in a reversible reaction, then equilibrium constant will

(A) depend on the concentration

(B) increase

(C) unchanged

(D) decrease

Answer: unchanged

12. Which of the following aqueous solutions will have highest pH?

(A) NaCl

(B) CH3COONa

(C) Na2CO3

(D) NH4Cl

Answer: Na2CO3

13. Which of the following mixtures in aqueous solution of equimolar concentration acts as a buffer solution?

(A) HNO3 and NaOH

(B) H2SO4 and KOH

(C) NH4OH(excess) + HCl

(D) CH3COOH and NaOH(excess)

Answer: NH4OH(excess) + HCl

14. Among the following hydroxides, the one which has the lowest value of Ksp at ordinary temperature (about 25°C) is

(A) Mg (OH)2

(B) Ca(OH)2

(C) Ba(OH)2

(D) Be(OH)2

Answer: Be(OH)2

15. Solubility of M2S salt is 3.5 × 10-6 then find out solubility product.

(A) 1.7 × 10-6

(B) 1.7 × 10-16

(C) 1.7 × 10-18

(D) 1.7 × 10-12

Answer: 1.7 × 10-16

16. What is the pH of a 0.10 M solution of barium hydroxide, Ba(OH)2 ?

(A) 11.31

(B) 11.7

(C) 13.30

(D) None of these

Answer: 13.30

17. A certain buffer solution contains equal concentration of X and HX. The ka for HX is 10-8. The pH of the buffer is

(A) 3

(B) 8

(C) 11

(D) 14

Answer: 8

18. Highest pH will be recorded for which of the following solutions if they are equimolar

(A) AlCl3

(B) BaCl2

(C) BeCl2

(D) LiCl

Answer: BaCl2

19. In 0.10 M aqueous solution of pyridine (C5H5N), find the percentage of pyridine that forms pyridinium ion (C5H5N+H) (Kb for C5H5N = 1.7 x 10-9)

(A) 1.6%

(B) 0.77%

(C) 0.0060%

(D) 0.013%

Answer: 0.013%

20. Which of the following aqueous solution will be the best conductor of electricity?

(A) NH3

(B) CH3COOH

(C) HCl

(D) C6H12O6

Answer: HCl

21. Find the conjugate acid of NH2

(A) NH3

(B) NH4OH

(C) NH4+

(D) NH2

Answer: NH3

22. What will be the pH of a buffer solution having an equal concentration of B and HB (Kb = 10-10 for B)

(A) 7

(B) 4

(C) 10

(D) 6

Answer: 4

23. Find the pH of a solution when 0.01 M HCl and 0.1 M NaOH are mixed in equal volumes

(A) 12.65

(B) 1.04

(C) 7.0

(D) 2.0

Answer: 12.65

24. For the reaction N2O4 (g)  2NO2 (g), the value of K is 50 at 400 K and 1700 at 500 K. Which of the following options is correct?

(A) The reaction is endothermic

(B) The reaction is exothermic

(C) If NO2 (g) and N2O4 (g) are mixed at 400 K at partial pressures 20 bar and 2 bar respectively, more N2O4 (g) will be formed.

(D) The entropy of the system increases.

Answer: A, C, D

25. Which of the following will produce a buffer solution when mixed in equal volumes?

(A) 0.1 mol dm–3 NH4OH and 0.1 mol dm–3 HCl

(B) 0.05 mol dm–3 NH4OH and 0.1 mol dm–3 HCl

(C) 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl

(D) 0.1 mol dm–3 CH4COONa and 0.1 mol dm–3 NaOH

Answer: 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl

26. The acidity of BF3 can be explained based on which of the following concepts?

(A) Arrhenius concept

(B) Bronsted Lowry concept

(C) Lewis concept

(D) Bronsted Lowry as well as Lewis concept.

Answer: Lewis concept

27. The solubility of Ca3(PO4)2 in water is y mol/L. Its solubility product is:

(A) 6y²

(B) 36 y4

(C) 64 y5

(D) 108 y5

Answer: 108 y5

28. The correct relationship between Ka1, Ka2 and Ka3 is

(A) Ka3 = Ka1 × Ka2

(B) Ka3 = Ka1 + Ka2

(C) Ka3 = Ka1 – Ka2

(D) Ka3 = Ka1 /Ka2

Answer: Ka3 = Ka1 × Ka2

29. The ionisation constant of an acid, Ka, is the measure of the strength of an acid. The Ka values of acetic acid, hypochlorous acid and formic acid are 1.74 × 10–5, 3.0 × 10–8 and 1.8 × 10–4 respectively. Which of the following orders of pH of 0.1 mol dm–3 solutions of these acids are correct?

(A) acetic acid > hypochlorous acid > formic acid

(B) hypochlorous acid > acetic acid > formic acid

(C) formic acid > hypochlorous acid > acetic acid

(D) formic acid > acetic acid > hypochlorous acid

Answer: formic acid > acetic acid > hypochlorous acid

30. The pH of neutral water at 25°C is 7.0. As the temperature increases, ionization of water increases, however, the concentration of H+ ions and OH– ions are equal. What will be the pH of pure water at 60°C?

(A) Equal to 7.0

(B) Greater than 7.0

(C) Less than 7.0

(D) Equal to zero

Answer: Less than 7.0

31. Which of the following will produce a buffer solution when mixed in equal volumes?

(A) 0.1 mol dm–3 NH4OH and 0.1 mol dm–3 HCl

(B) 0.05 mol dm–3 NH4OH and 0.1 mol dm–3 HCl

(C) 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl

(D) 0.1 mol dm–3 CH4COONa and 0.1 mol dm–3 NaOH

Answer: 0.1 mol dm–3 NH4OH and 0.05 mol dm–3 HCl

32. What will be the correct order of vapour pressure of water, acetone and ether at 30°C. Given that among these compounds, water has a maximum boiling Do point and ether have a minimum boiling point?

(A) Water < ether < acetone

(B) Water < acetone < ether

(C) Ether < acetone < water

(D) Acetone < ether < water

Answer: Water < acetone < ether

33. Which of the following options will be correct for the stage of half completion of the reaction A B

(A) ∆Gᶱ= 0

(B) ∆Gᶱ > 0

(C) ∆Gᶱ< 0

(D) ∆Gᶱ= –RT ln2.

Answer: ∆Gᶱ= 0

34. Ka for CH3COOH is 1.8 × 10–5 and Kb for NH4OH is 1.8 × 10–5. The pH of ammonium acetate will be

(A) 7.005

(B) 4.75

(C) 7.0

(D) Between 6 and 7

Answer: 7.0

35. What will be the value of pH of 0.01 mol dm–3 CH3COOH?

(A) 3.4

(B) 3.6

(C) 3.9

(D) 3.0

Answer: 3.4

36. In which of the following solvents is silver chloride most soluble?

(A) 0.1 mol dm–3 AgNO3 solution

(B) 0.1 mol dm–3 HCl solution

(C) H2O

(D) Aqueous ammonia

Answer: Aqueous ammonia

37. Concentration of the Ag+ ions in a saturated solution of Ag2C2O4 is 2.2 x 10-4 mol L-1. Solubility product of Ag2C2O42 is

(A) 2.66 × 10-12

(B) 4.5 × 10-11

(C) 5.3 × 10-12

(D) 2.42 × 10-8

Answer: 5.3 × 10-12

38. When equal volumes of 0.1 M NaOH and 0.01 M HCl are mixed, the hydroxide ion concentration is

(A) 7.0

(B) 1.04

(C) 12.65

(D) 2.0

Answer: 12.65

39. A weak acid HX has the dissociation constant 1 × 10-5 M. It forms a salt NaX on reaction with alkali. The degree of hydrolysis of 0.1 M solution of NaX is

(A) 0.0001%

(B) 0.01%

(C) 0.1%

(D) 0.15%

Answer: 0.01%

40. The pH of a 10-10 M NaOH solution is nearest to

(A) 10

(B) 7

(C) 4

(D) -10

Answer: 4

41. Which of the following oxides is not expected to react with sodium hydroxide?

(A) CaO

(B) SiO2

(C) BeO

(D) B2O3

Answer: CaO

42. What is the pH of a 0.10 M solution of barium hydroxide, Ba (OH)2?

(A) 11.31

(B) 11.7

(C) 13.30

(D) None of these

Answer: 13.30

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Chemical Equilibrium Questions and Answers with FREE PDF

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