CBSE Class 11 Chemistry Chemical Equilibrium MCQs Set A

Question: Which of the following is not a general characteristic of equilibria involving physical processes ?

a) All the physical processes stop at equilibrium

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

c) All measurable properties of the system remain constant.

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

Answer: All the physical processes stop at equilibrium

Question: The liquid which has a ____ vapour pressure is more volatile and has a_____boiling point.

a) Higher, lower

b) Higher , higher

c) Lower, lower

d) Lower, higher

Answer: Higher, lower

Question: Boiling point of the liquid depends on the atmospheric pressure. It depends on the altitude of the place; at high altitude the boiling point…………..

a) decreases

b) increases

c) either decreases or increases

d) remains same

Answer: decreases

Question: In an experiment three watch glasses containing separately 1mL each of acetone, ethyl alcohol, and water are exposed to atmosphere and the experiment with different volumes of the liquids in a warmer room is repeated, it is observed that in all such cases the liquid eventually disappears and the time taken for complete evaporation in each case was different. The possible reason is/are

a) All of the above

b) the temperature is different

c) the amount of the liquids is different

d) the nature of the liquids is different

Answer: All of the above

Question: A small amount of acetone is taken in a watch glass and it is kept open in atmosphere. Which statement is correct for the given experiment?

a) The rate of condensation from vapour to liquid state is much less than the rate of evaporation

b) The rate of condensation from vapour to liquid state is equal or less than the rate of evaporation.

c) The rate of condensation from vapour to liquid state is equal to the rate of evaporation

d) None of these

Answer: The rate of condensation from vapour to liquid state is much less than the rate of evaporation

Question: Reaction is said to be in equilibrium when

a) the rate of transformation of reactant to products is equal to the rate of transformation of products to the reactants.

b) 50% of the reactants are converted to products

c) the volume of reactants is just equal to the volume of the products

d) the reaction is near completion and all the reactants are converted to products

Answer: the rate of transformation of reactant to products is equal to the rate of transformation of products to the reactants.

Question: Which of the following is not true about a reversible reaction?

a) Number of moles of reactants and products is always equal

b) It can be attained only in a closed container

c) It cannot be influenced by a catalyst

d) The reaction does not proceed to completion

Answer: Number of moles of reactants and products is always equal

Question: If a system is at equilibrium, the rate of forward to the reverse reaction is

a) equal

b) less

c) high

d) at equilibrium

Answer: equal

Question: In a reversible chemical reaction having two reactants in equilibrium, if the concentration of the reactants are doubled then the equilibrium constant will

a) Remain the same

b) Be halved

c) Also be doubled

d) Become one-fourth

Answer: Remain the same

Question: On doubling P and V with constant temperature the equilibrium constant will

a) remain constant

b) become one-fourth

c) become double

d) None of these

Answer: remain constant

Question: The reaction quotient Q is used to

a) predict the direction of the reaction

b) calculate equilibrium concentrations

c) calculate equilibrium constant

d) predict the extent of a reaction on the basis of its magnitude

Answer: predict the direction of the reaction

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

a) Both

b) This theory was applicable to only aqueous solutions

c) This theory was applicable to all solutions

d) None of these

Answer: Both

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

a) No

b) Yes

c) Not known

d) Gaseous HCl does not exist

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: For the chemical reaction 3X(g) + Y(g) ⇌ X₃ Y(g),the amount of X₃ Y at equilibrium is affected by
a. Temperature and pressure
b. Temperature only
c. Pressure only
d. Temperature, pressure and catalyst
Answer : A

Question: In the reaction N₂ + 3H₂ → 2NH₃ , the product increases on:
a. Increasing temperature
b. Increasing pressure
c. Increasing temperature and pressure both
d. Decreasing temperature and pressure both
Answer : B

Question: In which of the following system, doubling the volume of the container cause a shift to the right:
a. H₂ (g) + Cl₂ (g) = 2HCl(g)
b. 2CO(g) + O₂ (g) = 2CO₂ (g)
c. N₂ (g) + 3H₂ (g) = 2NH₃ (g)
d. PCl₅ (g) ⇌ PCl₃ (g) + Cl₂ (g)
Answer : D

Question: The equilibrium SO₂ Cl_2(g) ⇌ SO_2(g) + Cl_2(g) is attained at 25°C in a closed container and an inert gas helium is introduced which of the following statement is correct:
a. More chlorine is formed
b. Concentration of SO₂ is reduced
c. More SO₂ Cl₂ is formed
d. Concentration of SO₂ Cl₂ , SO₂ and Cl₂ does not change
Answer : D

Question: Which of the following equilibria will shift to right side on increasing the temperature?

Answer : C

Question: h_2(g) + I_2(g) ⇌ 2HI_(g) ΔH = + q cal, then formation of HI:
a. Is favoured by lowering the temperature
b. Is favoured by increasing the pressure
c. Is unaffected by change in pressure
d. Is unaffected by change in temperature
Answer : C

Question: In which of the following equilibrium systems is the rate of the backward reaction favoured by increase of pressure?
a. PCl₅ ⇌ PCl₃ + Cl₂
b. 2SO₂ + O₂ ⇌ 2SO₃
c. N₂ + 3H₂ ⇌ 2NH₃
d. N₂ + O ⇌ 2NO
Answer : A

Question: Which of the following equilibrium is not shifted by increase in the pressure?
a. H_2(g) + I_2(g) ⇌ 2HI_(g)
b. N_2(g) + 3H_2(g) ⇌ 2NH_3(g)
c. 2CO(g) + O_2(g) ⇌ 2CO_2(g)
d. 2C_(S) + O_2(g) ⇌ 2CO_(g)
Answer : A

Question: According to Le–Chatelier’s principal adding heat to a solid and liquid in equilibrium with endothermic nature will cause the:
a. Temperature to rise
b. Temperature to fall
c. Amount of solid to decrease
d. Amount of liquid to decrease
Answer : C

Question: On addition of an inert gas at constant volume to the reaction N₂ + 3H ⇌ 2NH at equilibrium:
a. The reaction remains unaffected
b. Forward reaction is favoured
c. The reaction halts
d. Backward reaction is favoured
Answer : A

Question: N₂ O₄ ⇌ 2NO₂ ,K_c = 4. This reversible reaction is studied graphically as shown in the figure. Select the correct statements:

a. Reaction quotient has maximum value at point A
b. Reaction proceeds left to right at a point when [N₂ O₄ ] = [NO₂] = 0.1M
c. K_c = Q when point D or F is reached
d. Reaction quotient has minimum value at a point B
Answer : B, C, D

Question: Two gases A and B in the molar ratio 1:2 were admitted to an empty vessel and allowed to reach equilibrium at  400ºC and 8 atm pressure as A(g) + 2B(g) ⇌ 2C(g). The mole fraction of ‘C’ at equilibrium is 0.4. The correct statements are:
a. Equilibrium constant K_p 5/8 atm⁻¹
b. The pressure at equilibrium when mole fraction of A is 0.1 is 196 atm
c. Partial pressure of ‘C’ is 16/5 atm
d. Partial pressure of A is 4/5 atm
Answer : A, B, C

Question: For the dissociation N₂ O₅ (g) ⇌ 2NO₂ (g) + (1/2) O₂ (g)  if, M = Molecular mass of N₂ O₅ (g) D = Vapour density of equilibrium mixture P_o = Initial pressure of N₂ O₅ (g) Identify the ‘true’ statements:
a. Equilibrium pressure can be expressed as P⁰M/2D
b. Equilibrium pressure can be expressed as 2 P⁰D/M
c. Degree of dissociation can be expressed as P⁰ (M-2D)/3D
d. Increase in temperature will lower the magnitude of D
Answer : A, D