Chemical Kinetics PYQs Set 2 (PDF)

Set 2 of 11 · Questions 31-60 of 311

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Chemical Kinetics · Set 2 (Q31-60)
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31. $For the reaction of H_{2} with I_{2} the rate constant is 2.5 \times 10^{- 4} d m^{3} mo l^{- 1} s^{- 1} at 327° C and 1.0 d m^{3} mo l^{1} s^{- 1} at 527° C . The activation energy for the reaction, in kJ mo l^{- 1} is : (R = 8.314 J K^{- 1} mo l^{- 1})$ (1) $166$ (2) $150$ (3) $72$ (4) $59$ 32. $The reaction 2 X \to B is a zeroth orer reaction. If the initial concentration of X is 0.2 M, the half-life is 6 h. When the initial concentration of X is 0.5 M, the time required to reach its final concentration of 0.2 M will be :$ (1) $9.0 h$ (2) $12.0 h$ (3) $18.0 h$ (4) $7.2 h$ 33. $Which one of the following is a second order reaction?$ (1) $H_{2} + Br_{2} ⟶ 2 HBr$ (2) $NH_{4} NO_{3} ⟶ N_{2} + 3 H_{2} O$ (3) $H_{2} + Cl_{2} \to Sunlight 2 HCl$ (4) $CH_{3} COOCH_{3} + NaOH ⟶ CH_{3} COONa + H_{2} O$ 34. $The time required for 60 % completion of a first order reaction is 50 min . The time required for 93.6 % completion of the same reaction will be$ (1) $83.8 min$ (2) $50 min$ (3) $150 min$ (4) $100 min .$ 35. $A reaction has rate constant k = 2.4 \times 10^{- 4} s^{- 1} . Then, find the ratio of t_{99.9} to t_{50} .$ (1) $1$ (2) $5$ (3) $10$ (4) $15$ 36. $If the rate constant for a first order reaction is k, the time (t) required for the completion of 99 % of the reaction is given by$ (1) $t = \frac{4.606}{k}$ (2) $t = \frac{2.303}{k}$ (3) $t = \frac{0.693}{k}$ (4) $t = \frac{6.909}{k}$ 37. $Rate law for a reaction between A and B is given by r = k [A]^{n} [B]^{m} If concentration of A is doubled and concentration of B is halved from their initial value, the ratio of new rate of reaction to the initial rate of reaction (\frac{r _{2}}{r _{1}}) is$ (1) $(n - m)$ (2) $2^{(n - m)}$ (3) $\frac{1}{2 ^{m + n}}$ (4) $(m + n)$ 38. $The half-life period of a first order reaction at 300 K and 400 K are 50 s and 10 s respectively. The activation energy of the reaction in kJ mol^{- 1} is (log 5 = 0.70)$ (1) $4.0$ (2) $8.0$ (3) $16.10$ (4) $20.10$ 39. $Reaction A (g) \to 2 B (g) + C (g) is a first order reaction. It was started with pure A t / min Pressure of system at time t / mm Hg 10160 \infty 240 Which of the following option is incorrect?$ (1) $Initial pressure of A is 80 mm Hg$ (2) $The reaction never goes to completion$ (3) $Partial pressure of A after 10 minute is 40 mm Hg$ (4) $Rate constant of the reaction is 1.693 min^{- 1}$ 40. $The rate of a reaction doubles, when the temperature is changed from 300 K to 310 K . Activation energy of the change is_______((R = 8.314 JK^{- 1} mol^{- 1}, log 2 = 0.301)$ (1) $53.6 kJ mol^{- 1}$ (2) $48.6 kJ mol^{- 1}$ (3) $58.5 kJ mol^{- 1}$ (4) $60.5 kJ mol^{- 1}$ 41. $For the reaction 2 A + B ⟶ product, rate of the reaction is 15 \times 10^{- 2} mol dm^{- 3} sec^{- 1} . When [A] = 0.3 moldm^{- 3} and [B] = 0.05 mol dm^{- 3} . What is the value of rate constant if reaction is first order in both the reactants?$ (1) $5$ (2) $8$ (3) $10$ (4) $2$ 42. $For a first order reaction A \to Products, initial concentration of A is 0.1 M , which becomes 0.001 M after 5 minutes. Rate constant for the reaction in min^{- 1} is$ (1) $0.2303$ (2) $1.3818$ (3) $0.9212$ (4) $0.4606$ 43. $Calculate the molar mass of solute when 1.5 gram non volatile solute dissolved in 100 mL solvent having density 0.8 g mL^{- 1} lowers its freezing point by 0.75 K . (Freezing point depression constant for solvent is 5 K kg mol^{- 1})$ (1) $100 g mol^{- 1}$ (2) $125 g mol^{- 1}$ (3) $110 g mol^{- 1}$ (4) $75 g mol^{- 1}$ 44. $For the reaction, 2 A + B \to products, when the concentrations of A and B both were doubled, the rate of the reaction increased from 0.3 mol L^{- 1} s^{- 1} to 2.4 mol L^{- 1} s^{- 1} . When the concentration of A alone is doubled, the rate increased from 0.3 and L^{- 1} s^{- 1} to 0.6 mol L^{- 1} s^{- 1} . Which one of the following statements is correct ?$ (1) $Total order of the reaction is 4$ (2) $Order of the reaction with respect to B is 2$ (3) $Order of the reaction with respect to B is 1$ (4) $Order of the reaction with respect to A is 2$ 45. $The rate constant and half life of a first order reaction are related to each other as$ (1) $t_{1/2} = \frac{0.693}{k}$ (2) $t_{1/2} = 0.693 k$ (3) $k = 0.693 t_{1/2}$ (4) $k t_{1/2} = \frac{1}{0.693}$ 46. $The rate of a first order reaction doubles when the temperature changes from 300 K to 310 K . The activation energy of the reaction (in kJ mol^{- 1}) is (R (= 8.3 JK^{- 1} mol^{- 1}, log 2 = 0.3)$ (1) $43.33$ (2) $53.33$ (3) $63.33$ (4) $73.33$ 47. $A \to products, is a first order reaction. The time required to decompose A to half its initial amount is 60 minutes. The rate constant of the reaction (in s^{- 1}) is$ (1) $1.05 \times 10^{- 2}$ (2) $1.15 \times 10^{- 2}$ (3) $1.25 \times 10^{- 4}$ (4) $1.92 \times 10^{- 4}$ 48. $The rate constant for a zero order reaction A \to products is 0.0030 mol L^{- 1} s^{- 1} . How long it will take for the initial concentration of A to fall from 0.10 M to 0.075 M ?$ (1) $10$ (2) $20 s$ (3) $8.33 s$ (4) $1.33 s$ 49. $If a reaction follows the Arrhenius equation, the plot Ink vs \frac{1}{( RT )} gives staright line with a gradient (- y) unit. The energy required to activate the reactat is :$ (1) $y/R unit$ (2) $y unit$ (3) $yR unit$ (4) $-y unit$ 50. $Calculate the activation energy of a reaction, whose rate constant doubles on raising the temperature from 300 K to 600 K .$ (1) $3.45 kJ / mol$ (2) $6.90 kJ / mol$ (3) $9.68 kJ / mol$ (4) $19.6 kJ / mol$ 51. $For the reaction 5 Br^{-} (aq) + 6 H^{+} (aq) + BrO_{3}^{-} (aq) ⟶ 3 Br_{2} (aq) + 3 H_{2} O (l) if, - \frac{Δ ( BrO _{3}^{-} )}{Δ t} = 0.01 mol L^{- 1} min^{- 1}, \frac{Δ ( Br _{2} )}{Δ l} in mol L^{- 1} min^{- 1} is$ (1) $0.01$ (2) $0.3$ (3) $0.03$ (4) $0.005$ 52. $For a reaction \frac{1}{2} A ⟶ 2 B, rate of disappearance of A is related to rate of appearance of B by the expression$ (1) $\frac{- d [ A ]}{dt} = \frac{1}{4} \frac{d [ B ]}{dt}$ (2) $\frac{- d [ A ]}{dt} = 4 \frac{d [ B ]}{dt}$ (3) $\frac{- d [ A ]}{dt} = \frac{1}{2} \frac{d [ B ]}{dt}$ (4) $\frac{- d [ A ]}{dt} = \frac{d [ B ]}{dt}$ 53. $The rate equation for a reaction A \to B is r = k [A]^{0} . If the initial concentration of the reactant is a mol dm^{- 3}, the half life period of the reaction is$ (1) $k / a$ (2) $a / k$ (3) $2 a / k$ (4) $a /2 k$ 54. $The rate of first order reaction is 0.04 mol L^{- 1} s^{- 1} at 10 minutes and 0.03 mol L^{- 1} s^{- 1} at 20 minutes after initiation. Half life of the reaction is _____minutes. (Given log 2 = 0.3010, log 3 = 0.4771)$ 55. $For a reaction taking place in three steps at same temperature, overall rate constant K = \frac{K _{1} K _{2}}{K _{3}} . If Ea_{1}, Ea_{2} and Ea_{3} are 40,50 and 60 kJ / mol respectively, the overall Ea is______kJ / mol .$ 56. $For conversion of compound A \to B, the rate constant of the reaction was found to be 4. 6 x 1 0^{- 5} L m o l^{- l} s^{- 1} . The order of the reaction is______.$ 57. $The number of molecules with energy greater than the threshold energy for a reaction increases five fold by a rise of temperature from 27^{\circ} C to 42^{\circ} C . Its energy of activation in J / mol is (Take 5 = 1.6094; R = 8.314 Jmol^{- 1} K^{- 1})$ 58. $A sample of milk splits after 60 min. at 300 K and after 40 min. at 400 K when the population of lactobacillus acidophilus in it doubles. The activation energy (in kJmo l^{- 1}) for this process is closest to (Given, R = 8.3 Jmo l^{- 1} K^{- 1}, ln (\frac{2}{3}) = 0.4, e^{- 3} = 4.0)$ 59. $A reaction has a half life of 1 min. The timerequired for 99.9% completionof the reaction is ____ min. (Round off to the Nearest Integer) [Use: ln 2 = 0.69, ln 10 = 2.3]$ 60. $For a certain first order reaction32% of the reactant is left after 570s. The rate constant of this reaction is____\times 10^{- 3} s^{- 1} .(Round off to the Nearest Integer). [Given: log_{10} 2 = 0.301, ln 10 = 2.303]$