CBSE Class 11 Chemistry HOTs Equilibrium

Question. For the synthesis of ammonia by the reaction N₂ + 3H₂ ⇌ 2NH₃ in the Haber process, the attainment of equilibrium is correctly predicted by the curve

Answer : A

Question.PCl₅ is dissociating 50% at 250°C at a total pressure of P atm. If equilibrium constant is K_p, then which of the following relation is numerically correct –
(a) K_p = 3P
(b) P = 3K_p
(c) P = 2K_P/3
(d) K_p = 2P/3
Answer : B

Question.The value of Kp for the equilibrium reaction N₂O₄ (g) ⇌ 2NO₂ (g) is 2.
The percentage dissociation of N₂O₄(g) at a pressure of 0.5 atm is
(a) 25
(b) 88
(c) 50
(d) 71
Answer : D

Question.Two moles of PCl₅ were heated in a closed vessel of 2L. At equilibrium 40% of PCl₅ is dissociated into PCl₃ and Cl₂. The value of equilibrium constant is
(a) 0.53
(b) 0.267
(c) 2.63
(d) 5.3
Answer : B

Question.K₁ and K₂ are equilibrium constant for reactions (i) and (ii)
N₂(g) + O₂ (g) ⇌ 2 NO (g)                   ...(i)
NO(g) ⇌ (1/2) N₂ (g) + (1/2) O₂ (g)          ...(ii)
Then,
(a) K₁ = (1/K2)²
(b) K₁ = K₂²
(c) K₁ = 1/K₂
(d) K₁ = (K2)⁰
Answer : A

Question.For the decomposition of the compound, represented as NH₂COONH₄(s) ⇌ 2NH₃(g) + CO₂(g) the K_p = 2.9 × 10^–5 atm3. If the reaction is started with 1 mol of the compound, the total pressure at equilibrium would be :
(a) 1.94 × 10^–2 atm
(b) 5.82 × 10^–2 atm
(c) 7.66 × 10^–2 atm
(d) 38.8 × 10^–2 atm
Answer : B

Question.1.0 mole of AB₅(g) is placed in a closed container under one atmosphere and at 300K. It is heated to 600K, when 20% by mass of it dissociates as AB₅ (g) → AB(g) + 2 B₂ (g). The resultant pressure is
(a) 1.2 atm
(b) 2.4 atm
(c) 1.4 atm
(d) 2.8 atm
Answer : D

Question.For the reaction C(s) + CO₂(g) → 2CO(g), K_p = 63 atm at 1000 K. If at equilibrium : P_CO = 10
P_CO2, then the total pressure of the gases at equilibrium is
(a) 6.3 atm
(b) 6.93 atm
(c) 0.63 atm
(d) 0.693 atm
Answer : B

Question.The equilibrium constant for a reaction, N₂(g) + O₂(g) ⇆ 2NO(g) is 4 × 10^–4 at 2000 K. In the presence of catalyst, the equilibrium is attained 10 times faster. The equilibrium constant in presence of catalyst at 2000 K is :
(a) 10 × 10^–4
(b) 4 × 10^–2
(c) 4 × 10^–4
(d) 40 × 10^–4
Answer : C

Question.The figure shows the change in concentration of species A and B as a function of time.
The equilibrium constant K_c for the reaction

A(g) ⇌ 2B(g) is :
(a) Kc > 1
(b) K < 1
(c) K = 1
(d) data insufficient
Answer : A

Question. Air containing 79% of nitrogen and 21% of oxygen by volume is heated at 2200 K and 1 atm until equilibrium is established according to the reaction N₂(g) + O₂(g) ⇆ 2NO(g) If the K_P of the reaction is 1.1 × 10^–3, calculate the amount of nitric oxide produced in terms of volume percent.
(a) 1.67 %
(b) 1.23 %
(c) 1.33 %
(d) 1.54%
Answer : C

Question.At a certain temperature and 2 atm pressure equilibrium constant (KP) is 25 for the reaction SO₂ (g) + NO₂ (g) ⇆ SO₃ (g) + NO(g) Initially if we take 2 moles of each of the four gases and 2 moles of inert gas, what would be the equilibrium partial pressure of NO₂?
(a) 1.33 atm
(b) 0.1665 atm
(c) 0.133 atm
(d) None of these
Answer : C

Question.The degree of dissociation of acetic acid in a 0.1 M solution is 1.32 × 10^–2. Find out the dissociation constant of the acid.
(a) 1.50 × 10^–4
(b) 1.80 × 10^–16
(c) 1.76 × 10^–5
(d) 1.2 × 10^–3
Answer : C

Question.Among the following, the correct statement is:
(a) pH decreases when solid ammonium chloride is added to a dilute aqueous solution of NH₃
(b) pH decreases when solid sodium acetate is added to a dilute aqueous solution of acetic acid
(c) pH decreases when solid NaCl is added to a dilute aqueous solution of NaOH
(d) pH decreases when solid sodium oxalate is added to a dilute aqueous solution of oxalic acid
Answer : A

Question. For the manufacture of ammonia by the reaction N2 + 3H₂ ⇆ 2NH₃ + 2 kcal the favourable conditions are
(a) low temperature, low pressure and catalyst
(b) low temperature, high pressure and catalyst
(c) high temperature, low pressure and catalyst
(d) high temperature, high pressure and catalyst
Answer : B

Question.For the reaction XCO₃ (s) ⇆ XO(s) + CO₂ (g), K_p = 1.642 atm at 727°C. If 4 moles of XCO₃(s) was put into a 50 litre container and heated to 727°C. What mole percent of the XCO₃ remains unreacted at equilibrium?
(a) 20
(b) 25
(c) 50
(d) None of these
Answer : D

Question.Solubility products of CuI and Ag₂CrO₄ have almost the same value (~ 4 ´ 10^-12). The ratio of solubilities of the two salts (CuI:Ag₂CrO₄) is closest to
(a) 0.01
(b) 0.02
(c) 0.03
(d) 0.10
Answer : B

Question.At 25° C, the solubility product of Hg₂Cl₂ in water is 3.2 × 10^–17 mol³ dm^–9. What is the solubility of Hg₂Cl₂ in water at 25° C?
(a) 1.2 × 10^–12 M
(b) 3.0 × 10^–6 M
(c) 2 × 10^–6 M
(d) 1.2 × 10^–16 M
Answer : C

Question.Solid AgNO₃ is slowly added to a solution containing each of 0.01 M NaCl and 0.001 M NaBr.
What will be the concentration of Cl^– ions in solution when AgBr will just start to precipitate?
K_sp (AgBr) = 3.6 × 10^–13, K_sp (AgCl) = 1.8 × 10^–10.
(a) 1.8 × 10^–7
(b) 3.6 × 10^–10
(c) 0.01
(d) 2 × 1^0–4
Answer : C

Question.A buffered solution is prepared by mixing equal volumes of
(a) 0.2 M NH₄OH and 0.1 M HCl
(b) 0.2 M NH₄OH and 0.2 M HCl
(c) 0.2 M NaOH and 0.1 M CH₃COOH
(d) 0.1 M NH₄OH and 0.2 M HCl
Answer : A

Numeric Value Answer

Question. In the reaction PCl₅ ⇆ PCl₃ + Cl₂, the amount of each PCl₅, PCl₃ and Cl₂ is 2 mole at equilibrium and total pressure is 3 atm. What will be the value of K_p?
Answer : 1

Question.For the reaction : SnO₂(s)+2H₂(g) ⇆ 2H₂O(g) + Sn(s)
The value of 2 x K_P at 900 K where the equilibrium steam hydrogen mixture was 45% H₂ by volume is
Answer : 3

Question. A soft drink was bottled with a partial prssure of CO₂ of 3 bar over the liquid at room temperature. The partial pressure of CO₂ over the solution approaches a value of 30 bar when 44g of CO₂ is dissolved in 1 kg of water at room temperature. The approximate pH of the soft drink is ______ × 10_–1.
(First dissociation constant of H₂CO₃ = 4.0 × 10^–7; log 2 = 0.3; density of the soft drink = 1g mL^–1)
Answer : 3

Question.Calculate the pH at the equivalence point when a solution of 0.01 M CH₃COOH is titrated with a solution of 0.01 M NaOH. pKa of CH₃COOH is 4.74.
Answer : 8.22

Question.A buffer solution is prepared by mixing 0.1 M ammonia and 1.0 M ammonium chloride. At 298 K, the pK_b of NH₄OH is 5.0. The pH of the buffer is
Answer : 8

Question.If the solubility product of AB₂ is 3.20 × 10^–11M³, then the solubility of AB₂ in pure water is ______ × 10^–4 mol L^–1. 
[Assuming that neither kind of ion reacts with water]
Answer : 2.0

Question.Calculate pH of a resultant solution of 25 mL of 0.1 M HCl, 50 mL of 0.02 M HNO₃ and 25 mL of 0.1 M NaOH.
Answer : 2​​​​​​​

Question.Calculate the pOH of a solution at 25°C that contains 1 x 10^{– 10} M of hydronium ions, i.e. H₃O⁺.
Answer : 4

Question.For a reaction X + Y ⇆ 2Z, 1.0 mol of X, 1.5 mol of Y and 0.5 mol of Z were taken in a 1 L vessel and allowed to react. At equilibrium, the concentration of Z was 1.0 mol L^–1. The equilibrium constant of the reaction is . x/15 The value of x is _________.
Answer : 16

Question.0.1 M NaOH is titrated with 0.1 M HA till the end point; Ka for HA is 5.6 × 10^–6 and degree of hydrolysis is less compared to 1. Calculate pH of the resulting solution at the end point
Answer : 8.98