CHEMICAL KINETICS CLASS 12 SAMPLE QUESTION-2022

  1. In the reaction; A + 2B  3C + D, which of the following expression does not describe changes
    in the concentration of various species as a function of time :
    (A) {d [C] / dt} = – {3d [A] / dt} (B) {3d [D] / dt} = {d [C] / dt}
    (C) {3d [B] / dt} = – {2d [C] / dt} (D) {2d [B] / dt} = {d [A] / dt}
  2.  aA + bB  Product, dx/dt = k [A]a [B]b. If concentration of A is doubled, rate is four times. If
    concentration of B is made four times, rate is doubled. What is relation between rate of disappearance
    of A and that of B ?
    (A) – {d [A] / dt} = – {d [B] / dt} (B) – {d [A] / dt} = – {4 d [B] / dt}
    (C) – {4 d [A] / dt} = – {d [B]/ dt} (D) None of these
  3.  For the reaction H2 + Br2  2 HBr overall order is found to be 3/2. The rate of reaction can be
    expressed as:
    (A) [H2][Br2]1/2 (B) [H2]1/2 [Br2] (C) [H2]3/2 [Br2]0 (D) All of these
  4.  For rate constant is numerically the same for three reactions of first, second and third order
    respectively. Which of the following is correct :
    (A) if [A] = 1 then r1 = r2 = r3 (B) if [A] < 1 then r1 > r2 > r3
    (C) if [A] > 1 then r3 > r2 > r1 (D) All
  5. For the irreversible process, A + B  products, the rate is first–order w.r.t. A and second–
    order w.r.t. B. If 1.0 mol each of A and B introduced into a 1.0 L vessel, and the initial rate was 1.0
    × 10–2 mol L–1 s–1 , rate when half reactants have been turned into products is :
    (A) 1.25 × 10–3 mol L–1 s–1 (B) 1.0 × 10–2 mol L–1 s–1
    (C) 2.50 × 10–3 mol L–1 s–1 (D) 2.0 × 10–2 mol L–1 s–1
  6.  In a certain reaction, 10% of the reactant decomposes in one hour, 20 % in two hours, 30% in three
    hours and so on the dimensions of the rate constant is :
    (A) hour–1 (B) mole litre–1 sec–1 (C) litre mole–1 sec–1 (D) mole sec–1
  7.  The rate constant for the reaction A  B is 2 × 10–4 It. mol–1 min–1. The concentration of A at
    which rate of the reaction is (1/12) × 10–5 M sec–1 is :
    (A) 0.25 M (B) (1/20) 5/3M (C) 0.5 M (D) None of these
  8. What will be the order of reaction and rate constant for a chemical
    change having log t50% vs log concentration of (A) curves as :
    (A) 0, 1/2 (B) 1, 1
    (C) 2, 2 (D) 3, 1
  9. Two substances A (t1/2 = 5 min) and B (t1/2 = 15 min) are taken in such a way that initially
    [A] = 4[B]. The time after which both the concentration will be equal is : (Assume that reaction is
    first order)
    (A) 5 min (B) 15 min
    (C) 20 min (D) concentration can never be equal
  10. If a I-order reaction is completed to the extent of 60% and 20% in time intervals, t1 and t2, what is
    the ratio, t1 : t2 ?
    (A) 6.32 (B) 5.58 (C) 4.11 (D) 8.33
  11. A drop of solution (volume 0.05 mL) contains 3.0 × 10–6 moles of H+. If the rate constant of
    disappearance of H+ is 1.0 × 107 mole litre–1 sec–1. How long would it take for H+ in drop to
    disappear:
    (A) 6 × 10–8 sec (B) 6 × 10–7 sec (C) 6 × 10–9 sec (D) 6 × 10–10 sec
  12. 28. In a gaseous state reaction, A2 (g)  B(g) + (1/2)C (g), The increase in pressure from 100 mm
    to 120 mm is notices in 5 minutes. The rate of disapearance of A2 in mm min–1 is :
    (A) 4 (B) 8 (C) 16 (D) 2
  13.  Consider the reaction 2A(g)  3B(g) + C(g). Starting with pure A initially, the total pressure
    doubled in 3 hrs. The order of the reaction might possibly be
    (A) zero (B) first
    (C) second (D) unpredictable from this data
  14.  Formation of NO2F from NO2 and F2 as per the reaction 2NO2(g) + F2(g)  2NO2F(g) is a
    second order reaction, first order with respect to NO2 and first order with respect to F2. If NO2
    and F2 are present in a closed vessel in ratio 2 :1 maintained at a constant temperature with an
    initial total pressure of 3 atm, what will be the total pressure in the vessel after the reaction is
    complete?
    (A) 1atm (B) 2 atm (C) 2.5 atm (D) 3 atm
  15. In the reaction NH4NO2 (aq.)  N2 (g) + 2 H2O (l) the volume of N2 after 20 min and after a long
    time is 40 ml and 70 ml respectively. The value of rate constant is :
    (A) (1/20) In (7/4) min–1 (B) (2.303 /1200) log (7/3) sec–1
    (C) (1/20) log (7/3) min–1 (D) (2.303 / 20) log (11/7) min–1
  16. Rate of which reactions increases with temperature:
    (A) of any (B) of exothermic reactions
    (C) of endothermic (D) of none
  17. For a zero order reaction. Which of the following statement is false :
    (A) the rate is independent of the temperature of the reaction.
    (B) the rate is independent of the concentration of the reactants.
    (C) the half life depends upon the concentration of the reactants.
    (D) the rate constant has the unit mole It–1 sec–1.
  18. A large increase in the rate of a reaction for a rise in temperature is due to
    (A) increase in the number of collisions
    (B) the increase in the number of activated molecules
    (C) The shortening of mean free path
    (D) the lowering of activation energy
  19. How much faster would a reaction proceed at 25°C than at 0°C if the activation energy is 65 kJ?
    (A) 2 times (B) 5 times (C) 11 times (D) 16 times
  20. For a given reaction, energy of activation for forward reaction (Eaf) is 80kJ.mol1. H = 40kJ.
    mol1 for the reaction. A catalyst lowers Eaf to 20 kJ.mol1. The ratio of energy of activation for
    reverse reaction before and after addition of catalyst is :
    (A) 1.0 (B) 0.5 (C) 1.2 (D)2.0

 

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