Ecat Entry Test Chemistry Chemical Equilibrium MCQs

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Chemical equilibrium, Types of Chemical Equilibrium, Change in Concentration, Change in Pressure, Change in Temperature.

A reversible reaction at chemical equilibrium maintains a state of dynamic stability since both forward and reverse reaction rates become equal to each other. The reaction continues even though reactant and product concentrations stay fixed at the equilibrium state level. External factors including concentration as well as pressure and temperature all affect the state of equilibrium. The knowledge of Chemistry chemical equilibrium stands fundamental to solving problems appearing in industrial chemistry fields alongside biological processes and tests for ECAT admission.

Ecat Entry Test Chemistry Chemical Equilibrium MCQs

Types of Chemical Equilibrium

1. Dynamic Equilibrium

Under dynamic equilibrium, the forward and reverse reactions persist at equal speeds throughout. Gaseous reactions such as these exhibit this equilibrium type.

N2 ​ +3H2 ​ ⇌2NH3 ​

The formation of ammonia (NH₃) does not stop the reaction between nitrogen (N₂) and hydrogen (H₂) proceeding in the opposite direction.

2. Static Equilibrium

Static equilibrium appears as if no reaction is occurring, but at the molecular level, particles remain in balance. It is more common in physical processes like phase changes.

Factors Affecting Chemistry Chemical Equilibrium

1. Change in Concentration

According to Le Chatelier’s Principle, increasing the concentration of reactants shifts equilibrium forward, while increasing products shifts it backward. Example:

CO+2H2 ​ ⇌ CH3OH

Adding more CO or H₂ shifts the reaction towards methanol (CH₃OH) formation.

2. Change in Pressure

Pressure changes significantly impact gaseous equilibria. If the pressure increases, the equilibrium shifts toward the side with fewer gas molecules to reduce pressure. For example:

N2 ​ +3H2 ​ ⇌2NH3 ​

Since the right side has fewer molecules (2 vs. 4), increased pressure favors NH₃ formation.

3. Change in Temperature

  • If a reaction is exothermic (-ΔH), lowering the temperature favors the forward reaction (product formation).
  • If a reaction is endothermic (+ΔH), increasing the temperature favors the forward reaction.
    Example: 2SO2 ​ +O2 ​ ⇌2SO3 ​ ΔH=−188.3 kJ/mol

Increasing temperature reduces SO₃ yield because it shifts equilibrium towards reactants.

MCQs for ECAT Chemistry Chemical Equilibrium

1. Which of the solution among the following has highest pH?

  • 0.01 M NaHCO₃
  • 0.1 M H₂SO₄
  • 0.02 M CH₃COONa
  • 0.01 M NaOH
    correct

2. For which system does the equilibrium constant Kc has units of (concentration)¯¹?

  • 2HF = H₂ + F₂
  • H₂ + 3H₂ = 2NH₃
  • 2NO₂ = N₂O₄
    correct
  • H₂ + I₂ = 2HI

3. Which statement about the following equilibrium is correct? 2SO₂(g) + O₂(g) ≈2SO₃(g) ∆H≈ – 188.3 kJmol¯¹

  • The value of Kp falls with the rise in temperature
    correct
  • Adding V₂O₅ catalyst increases the equilibrium yield of SO₃
  • The value of Kp is equal to Kc
  • The value of Kp falls with increasing pressure

4. The pH of buffer solution is 4.74. On adding 0.1 ml (0.00001M) HC1 solution, the pH of solution will be:

  • 5.2
  • 5.3
  • 4.74
    correct
  • 4.7

5. 0.1 M HCI has pH = 1.0, it is about 100 times stronger than acetic acid. Then pH of acetic acid will be:

  • 1.3
  • 3correct
  • 2.0
  • 0.1

6. The solubility product of AgCI is 2 x 10¯¹⁰ mol² dm¯⁶. The maximum concentration of Ag⁺ in the solution is:

  • 2 x 10¯¹⁰ mol dm¯³
  • 1 x 10¯¹⁰ mol dm¯³
  • 1.41 x 10¯⁵ mol dm¯³
    correct
  • 2 x 10¯²⁰ mol dm¯³

7. Who studied the effect of temperature on equilibrium?

  • Lewis
  • Vant Hoff
    correct
  • Arrhenius
  • Van der Waal

8. The pH of 10¯³ mol dm ¯³ of an aqueous solution of H₂OS₄ is

  • 3.0
  • 2.7
    correct
  • 1.5
  • 2.0

9. Who introduced the term pH?

  • Henderson
  • Goldstein
  • Sorenson
    correct
  • Thomson

10. Chemical equilibrium involving reactants and products is more than one phase is known:

  • Dynamic
  • Static
  • Heterogeneous
    correct
  • Homogeneous

11. Neutralization of a strong acid with a strong base is:

  • None-spontaneous reaction
  • Reversible process
  • Chemical equilibrium
    correct
  • Spontaneous reaction

12. All of the following are the postulates of Arrhenius theory of ionization except:

  • Ionization is reversible process
  • Strong electrolyte ionize to a greater extent in water
    correct
  • Electrolyte ionize in water to produce cations and anions
  • Electrical conductivity of a solution of an electrolyte depends on the extent to which the electrolyte ionize in solution

13. The value of Kp is greater than Kc for a gaseous reaction when

  • Number of molecules of products is greater than those of reactants
    correct
  • Catalyst is added
  • Number of molecules of reactants is greater than those of products
  • Number of molecules of reactants and products are equal

14. Law of mass action states that rate of chemical reaction is directly proportional to the product of active masses of the reactants. The term active mass means

  • Number of moles per dm³ of reactants
    correct
  • Mass in grams converted to products
  • Total pressures of the reactants
  • Number of moles

15. If the difference of pKa values of the two acids is 2, then:

  • Acid with greater pKa is 10 times stronger acid
  • Acid with smaller pKa is 10 times stronger acid
  • Acid with greater pKa is 100 times stronger acid
  • Acid with smaller pKa is 100 times stronger acid
    correct

16. The value of Kp is greater than Kc for a gaseous reaction when

  • A catalyst is added
  • Number of molecules of products is greater than that the reactantscorrect
  • Number of molecules of products is greater than the reactants
  • Number of molecules of reactants is greater than those of products

17. Le-Chatelier’s principle is applied on the reversible reactions in order to:

  • Predict the reaction of reaction
  • Determine the rate reaction
  • Determine the extent of reaction
  • Find the best condition of favorable shifting the position of equilibriumcorrect

18. An excess of aqueous silver nitrate is added to aqueous barium chloride and precipitate is removed by filtration. What are the main ions in the filtrate?

  • Ba²⁺ and NO¯₃ only
  • Ag⁺ and NO¯₃ only
  • Ag⁺ and Ba⁺⁺ and NO¯₃
    correct
  • Ba²⁺ and NO¯₃ and CI¯₃

19. The ionic product of solution is greater than solubility product. The solution is:

  • None of all
  • Supersaturated
    correct
  • Saturate
  • Unsaturated

20. What is the unit of equilibrium constant kc for the following reaction? H₂ + I₂ Ĝ ≈ 2HI

  • Mol¯¹ dm³
  • None of thesecorrect
  • Mol¯² dm³
  • Mol dm¯¹

21. The strongest base among the following is

  • RbOH
    correct
  • NaCH
  • LiOH
  • KOH

22. The rate at which a substance reacts is directly proportional to its active mass and the rate of reaction is directly proportional to the product of the active masses of reacting substances in knows as?

  • Law of conservation of energy
  • Le-Chatelier’s principle
  • None of all
  • Law of mass action
    correct

23. Hydrogen gas and iodine vapours combine to form HI at 425°C. The same composition of mixture is present if we start with decomposition of HI. It suggests.

  • A static equilibrium
  • A dynamic equilibrium
    correct
  • Irreversible reaction
  • Law of mass action

24. Which is not true about buffer is a solution?

  • Whose pH is constant
  • Which resists change in its pH
  • Which resists enough to maintain its pH
  • Whose pH may or may not change during a chemical reactioncorrect

25. When rate of forward reaction is equal to rate of backward reaction, then the equilibrium established is called:

  • Chemical equilibrium
  • Dynamic equilibrium
    correct
  • Static equilibrium
  • None of all

Conclusion

Chemistry chemical equilibrium is crucial in industrial reactions, biological processes, and chemical engineering. Understanding its types and the effects of concentration, pressure, and temperature helps predict reaction behavior. For ECAT entry tests, mastering equilibrium principles and MCQs ensures a strong foundation in chemistry concepts.

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