CBSE Class 11 Chemistry VBQs Equilibrium

Question. In liquid-gas equilibrium, the pressure of vapours above the liquid is constant at
(a) constant temperature
(b) low temperature
(c) high temperature
(d) none of these.
Answer. A

Question. If K₁ and K₂ are the respective equilibrium constants for the two reactions,
XeF_6(g) + H₂O_(g) → XeOF_4(g) + 2HF_(g)
XeO_4(g) + XeF_6(g) → XeOF_4(g) + XeO₃F_2(g),the equilibrium constant of the reaction,
XeO_4(g) + 2HF_(g) → XeO₃F_2(g) + H₂O_(g), will be
(a) K₁/K₂
(b) K₁·K₂
(c) K₁/(K₂)²
(d) K₂/K₁
Answer. D

Question. The reaction, 2A_(g) + B_(g) ⇔ 3C_(g) + D_(g) is begun with the concentrations of A and B both at an initial value of 1.00 M. When equilibrium is reached, the concentration of D is measured and found to be 0.25 M. The value for the equilibrium constant for this reaction is given by the expression
(a) [(0.75)³(0.25)] ÷ [(1.00)²(1.00)]
(b) [(0.75)³(0.25)] ÷ [(0.50)²(0.75)]
(c) [(0.75)³(0.25)] ÷ [(0.50)²(0.25)]
(d) [(0.75)³(0.25)] ÷ [(0.75)²(0.25)] 
Answer. B

Question. The dissociation equilibrium of a gas AB₂ can be represented as :
 2AB_2(g) ⇔ 2AB_(g) + B_2(g)
The degree of dissociation is x and is small compared to 1. The expression relating the degree of dissociation (x) with equilibrium constant K_p and total pressure P is
(a) (2K_p/P)^1/2
(b) (K_p/P)
(c) (2K_p/P)
(d) (2K_p/P)^1/3 
Answer. D

Question. The values of K_p1 and K_p2 for the reactions,
X ⇔ Y + Z ...(i)
A ⇔ 2B ...(ii)
are in the ratio 9 : 1. If degree of dissociation of X and A be equal, then total pressure at equilibrium (i) and (ii) are in the ratio
(a) 36 : 1
(b) 1 : 1
(c) 3 : 1
(d) 1 : 9
Answer. A

Question. A 20 litre container at 400 K contains CO_2(g) at pressure 0.4 atm and an excess of SrO (neglect the volume of solid SrO). The volume of the container is now decreased by moving the movable piston fitted in the container. The maximum volume of the container, when pressure of CO₂ attains its maximum value, will be
(Given that : SrCO_3(s) ⇔SrO(s) + CO_2(g),Kp = 1.6 atm)
(a) 10 litre
(b) 4 litre
(c) 2 litre
(d) 5 litre 
Answer. D

Question. In which of the following equilibrium Kc and Kp are not equal?
(a) 2NO_(g) ⇔ N_2(g) + O_2(g)
(b) SO_2(g) + NO_2(g) ⇔ SO_3(g) + NO_(g)
(c) H_2(g) + I_2(g) ⇔ 2HI_(g)
(d) 2C_(s) + O_2(g) ⇔ 2CO_2(g)
Answer. D

Question. If the concentration of OH– ions in the reaction
Fe(OH)_3(s) ⇔ Fe³⁺ _(aq) + 3OH^– _(aq) is decreased by 1/4 times, then equilibrium concentration of Fe³⁺ will increase by
(a) 64 times
(b) 4 times
(c) 8 times
(d) 16 times.
Answer. A

Question. If the value of equilibrium constant for a particular reaction is 1.6 × 10¹², then at equilibrium the system will contain
(a) mostly products
(b) similar amounts of reactants and products
(c) all reactants
(d) mostly reactants. 
Answer. A

Question. In Haber process, 30 litres of dihydrogen and 30 litres of dinitrogen were taken for reaction which yielded only 50% of the expected product. What will be the composition of gaseous mixture under the aforesaid condition in the end?
(a) 20 litres ammonia, 20 litres nitrogen, 20 litres hydrogen
(b) 10 litres ammonia, 25 litres nitrogen, 15 litres hydrogen
(c) 20 litres ammonia, 10 litres nitrogen, 30 litres hydrogen
(d) 20 litres ammonia, 25 litres nitrogen, 15 litres hydrogen
Answer. B

Question. Hydrolysis of sucrose is given by the following
reaction : Sucrose + H₂O ⇔ Glucose + Fructose
If the equilibrium constant (KC) is 2 × 10¹³ at 300 K, the value of ΔrG° at the same temperature will be
(a) –8.314 J mol^–1K^–1 × 300 K × ln(2 × 10¹³)
(b) 8.314 J mol^–1K^–1 × 300 K × ln(2 × 10¹³)
(c) 8.314 J mol^–1K^–1 × 300 K × ln(3 × 10¹³)
(d) –8.314 J mol^–1K^–1 × 300 K × ln(4 × 10¹³)
Answer. A

Question. Which of the following statements is correct for a reversible process in a state of equilibrium?
(a) ΔG° = –2.30 RT log K
(b) ΔG° = 2.30 RT log K
(c) ΔG = –2.30 RT log K
(d) ΔG = 2.30 RT log K 
Answer. A

Question. Which one of the following conditions will favour maximum formation of the product in the reaction
A_2(g) + B_2(g) ⇔  X_2(g), DrH = –X kJ ?
(a) Low temperature and high pressure
(b) Low temperature and low pressure
(c) High temperature and high pressure
(d) High temperature and low pressure
Answer. A

Question. For the reversible reaction,
N_2(g) + 3H_2(g)  ⇔  2NH_3(g) + heat
The equilibrium shifts in forward direction
(a) by increasing the concentration of NH_3(g)
(b) by decreasing the pressure
(c) by decreasing the concentrations of N_2(g) and H_2(g)
Answer. D

Question. KMnO₄ can be prepared from K₂MnO₄ as per the reaction, 3MnO₄^2– + 2H₂O ⇔ 2MnO₄ – + MnO₂ + 4OH^–
The reaction can go to completion by removing OH^– ions by adding
(a) CO₂
(b) SO₂
(c) HCl
(d) KOH
Answer. A

Question. The value of DH for the reaction X_2(g) + 4Y_2(g) ⇔ 2XY_4(g) is less than zero.
Formation of XY_4(g) will be favoured at
(a) high temperature and high pressure
(b) low pressure and low temperature
(c) high temperature and low pressure
(d) high pressure and low temperature
Answer. D

Question. Reaction BaO_2(s)  ⇔ BaO_(s) + O_2(g); DH = +ve. In equilibrium condition, pressure of O₂ depends on
(a) increase mass of BaO₂
(b) increase mass of BaO
(c) increase temperature on equilibrium
(d) increase mass of BaO₂ and BaO both.
Answer. C

Question. For any reversible reaction, if we increase concentration of the reactants, then effect on equilibrium constant
(a) depends on amount of concentration
(b) unchange
(c) decrease
(d) increase. 
Answer. B

Question. According to Le Chatelier’s principle, adding heat to a solid and liquid in equilibrium will cause the
(a) temperature to increase
(b) temperature to decrease
(c) amount of liquid to decrease
(d) amount of solid to decrease.
Answer. D

Question. Which one of the following information can be obtained on the basis of Le Chatelier principle?
(a) Dissociation constant of a weak acid
(b) Entropy change in a reaction
(c) Equilibrium constant of a chemical reaction
(d) Shift in equilibrium position on changing value of a constraint
Answer. D

Question. Aqueous solution of which of the following compounds is the best conductor of electric current?
(a) Hydrochloric acid, HCl
(b) Ammonia, NH₃
(c) Fructose, C₆H₁₂O₆
(d) Acetic acid, C₂H₄O₂ 
Answer. A

Question. Aqueous solution of acetic acid contains
(a) CH₃COO^– and H⁺
(b) CH₃COO^–, H₃O⁺ and CH₃COOH
(c) CH₃COO^–, H₃O⁺ and H⁺
(d) CH₃COOH, CH₃COO^– and H⁺
Answer. B

Question. Conjugate base for Bronsted acids H2O and HF are
(a) H₃O⁺ and H₂F⁺, respectively
(b) OH^– and H₂F⁺, respectively
(c) H₃O⁺ and F^–, respectively
(d) OH^– and F^–, respectively. 
Answer. D

Question. Which of the following cannot act both as Bronsted acid and as Bronsted base ?
(a) HCO₃^–
(b) NH₃
(c) HCl
(d) HSO^–
Answer. C

Question. Which of the following fluoro-compounds is most likely to behave as a Lewis base?
(a) BF₃
(b) PF₃
(c) CF₄
(d) SiF₄
Answer. B

Question. Which of these is least likely to act as a Lewis base?
(a) BF₃
(b) PF₃
(c) CO
(d) F^–
Answer. A

Question. Which is the strongest acid in the following?
(a) HClO₄
(b) H₂SO₃
(c) H₂SO₄
(d) HClO₃ 
Answer. A

Question. Which one of the following molecular hydrides acts as a Lewis acid?
(a) NH₃
(b) H₂O
(c) B₂H₆
(d) CH₄ 
Answer. C

Question. Which of the following molecules acts as a Lewis acid?
(a) (CH₃)₂O
(b) (CH₃)₃P
(c) (CH₃)₃N
(d) (CH₃)₃B
Answer. D

Question. Which one of the following statements is not true?
(a) Among halide ions, iodide is the most powerful reducing agent.
(b) Fluorine is the only halogen that does not show a variable oxidation state.
(c) HOCl is a stronger acid than HOBr.
(d) HF is a stronger acid than HCl. 
Answer. D

Question. Which one of the following compounds is not a protonic acid?
(a) B(OH)₃
(b) PO(OH)₃
(c) SO(OH)₂
(d) SO₂(OH)₂
Answer. A

Question. In HS^–, I^–, R – NH₂, NH₃ order of proton accepting tendency will be
(a) I^– > NH₃ > R – NH₂ > HS^–
(b) NH₃ > R – NH₂ > HS^– > I^–
(c) R – NH₂ > NH₃ > HS^– > I^–
(d) HS^– > R – NH₂ > NH₃ > I^–
Answer. C

Question. Conjugate acid of NH₂^– is
(a) NH₄OH
(b) NH₄⁺
(c) NH₂^–
(d) NH₃ 
Answer. D

Question. Which compound is electron deficient?
(a) BeCl₂
(b) BCl₃
(c) CCl₄
(d) PCl₅ 
Answer. B

Question. The strongest conjugate base is
(a) SO₄^2–
(b) Cl^–
(c) NO₃^–
(d) CH₃COO^– 
Answer. D

Question. Which of the following is not a Lewis acid?
(a) SiF₄
(b) C₂H₄
(c) BF₃
(d) FeCl₃ 
Answer. B

Question. Repeated use of which one of the following fertilizers would increase the acidity of the soil?
(a) Ammonium sulphate
(b) Superphosphate of lime
(c) Urea
(d) Potassium nitrate
Answer. A

1. In group III, the cat ions Fe, Cr and Al are precipitated as hydroxides by the addition of NH₄OH to the aqueous solution of the mixture. But a small amount of NH₄Cl is added before the addition of NH₄ OH. Arvinder was confused to see why common NH4+ ion is added? He asked his friend Palvinder the purpose of adding common NH4+ ion. Palvinder explained the purpose of adding NH₄Cl and then Arvinder got satisfied.

(a) What would be the answer of Palvinder.

(b) Why magnesium is not precipitated from a solution of it’s a salt by NH₄OH in the presence of NH₄Cl.

(c) What values are shown by Palvinder?

(2) There is a fizz when a soda water battle is opened. Kusum was very curious to know its reason. She discussed her problem with her elder sister Monika. Monika explained Kusum the whole phenomenon and then Kusum got satisfied.

(a) What would be the answer of Monika?

(b) Solubility of a Ca (CH₃COO)₂ decreases with rise of temperature while that of Pb (NO₃)₂ increases with rise of temperature.

(c) What values are shown by Kusum and Monika?

3. A solution has the capacity to resist the change in its PH when a small amount of a strong acid or strong base is added to it. These solutions may be acidic or basic or neutral in nature.

(a) Name this solution and give a general example.

(b) Select the components to prepare this type of solution having PH between 4 and5.