Chemical Kinetics PYQs Set 7 (PDF)

Set 7 of 11 · Questions 181-210 of 311

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Chemical Kinetics · Set 7 (Q181-210)
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181. $If benzene diazonium chloride undergoes first order decomposition at T (K) with a rate constant of 6.93 \times 10^{- 2} min^{- 1}, the time for completion of 90 % of the reaction (in min) is (nearest integer) (log 2 = 0.30, log 3 = 0.477)$ (1) $15$ (2) $30$ (3) $33$ (4) $43$ 182. $A first order reaction has the rate constant of 1.15 \times 10^{- 3} s^{- 1} . The time required to reduce 10 g of reactant to 6 g is x \times 10^{2} sec . What is the approximate value of x ? (log 5 = 0.7, log 3 = 0.48)$ (1) $2.2$ (2) $3.3$ (3) $4.4$ (4) $1.1$ 183. $For the reaction 2 A + 3 B + \frac{3}{2} C \to 3 P which statement is correct?$ (1) $\frac{d n _{A}}{dt} = \frac{3}{2} \frac{dn _{B}}{dt} = \frac{3}{4} \frac{dn _{C}}{dt}$ (2) $\frac{dn _{A}}{dt} = \frac{dn _{B}}{dt} = \frac{dn _{C}}{dt}$ (3) $\frac{dn _{A}}{dt} = \frac{2}{3} \frac{dn _{B}}{dt} = \frac{4}{3} \frac{dn _{C}}{dt}$ (4) $\frac{dn _{A}}{dt} = \frac{2}{3} \frac{dn _{B}}{dt} = \frac{3}{4} \frac{dn _{C}}{dt}$ 184. $A reaction, 3 X (g) \to 2 Y (g) + Z (g) takes place in a closed vessel. What is the rate of formation of Y (in mol L^{- 1}) if the rate of disappearance of X is 7.2 \times 10^{- 3} mol L^{- 1} s^{- 1} ?$ (1) $3.6 \times 10^{- 3}$ (2) $4.8 \times 10^{- 3}$ (3) $2.4 \times 10^{- 3}$ (4) $1.2 \times 10^{- 3}$ 185. $Which statement among the following is incorrect?$ (1) $Unit of rate of disappearance is M s^{- 1} .$ (2) $Unit of rate of reaction is M s^{- 1} .$ (3) $Unit of rate constant k depends upon order of reaction.$ (4) $Unit of rate constant k for a first order reaction is M s^{- 1} .$ 186. $Consider a gas phase reaction which occurs in a closed vessel 2 A \to 4 B + C The concentration of B is found to be increased by 5 \times 10^{- 3} mol L^{- 1} in 10 seconds. The rate of disappearance of A (in mol L^{- 1} s^{- 1}) is$ (1) $4.75 \times 10^{- 4}$ (2) $7.5 \times 10^{- 4}$ (3) $1.25 \times 10^{- 4}$ (4) $2.5 \times 10^{- 4}$ 187. $The reaction A_{2} + B_{2} \to 2 AB follows the mechanism A_{2} k_{1} k_{- 1} A + A (fast) A + B_{2} \to k_{2} AB + B (slow) AB + B \to AB (fast) The overall order of the reaction is:$ (1) $2$ (2) $2.5$ (3) $3$ (4) $1.5$ 188. $20 % of a first order reaction was found to be completed at 10:00 a.m at 11.30 a . m . on the same day, 20 % of the reaction was found to be remaining. The half life period in minutes of the reaction is$ (1) $90$ (2) $45$ (3) $60$ (4) $30$ 189. $In collision theory of chemical reaction, Z_{AB} represents$ (1) $The collision frequency of reactants, A and B$ (2) $Steric factor$ (3) $The fraction of molecules with energies equal to$ (4) $The fraction of molecules with energies greater than$ 190. $For a reaction A + 2 B \to Products, when concentration of B alone is increased, half life remains the same. If concentration of A alone is doubled, rate remains the same. The unit of rate constant for the reaction is$ (1) $s^{- 1}$ (2) $1.mol^{- 1} s^{- 1}$ (3) $molL-1 s^{- 1}$ (4) $atm^{- 1}$ 191. $An increase in the concentration of the reactants of a reaction leads to change in :$ (1) $Heat of reaction$ (2) $Threshold energy$ (3) $Collision frequency$ (4) $Activation energy$ 192. $For a zero order reaction, the plot of concentration of reactant vs time is (Hint: Consider the intercept on the concentration axis)$ (1) $linear with +ve slope and non zero +ve intercept$ (2) $linear with -ve slope and non zero + ve intercept$ (3) $linear with -ve slope and zero intercept$ (4) $linear with + ve slope and zero intercept$ 193. $Given above is the concentration vs time plot for a dissociation reaction: A \to nB . Based on the data of the initial phase of the reaction (initial 10 min), the value of n is____.$ (1) $3$ (2) $2$ (3) $4$ (4) $5$ 194. $The rate of the reaction, 2 N O + C l_{2} \to 2 N O C l is given by the rate equation rate = k [N O]^{2} [C l_{2}] . The value of the rate constant can be increased by$ (1) $increasing the temperature$ (2) $increasing the concentration of NO$ (3) $increasing the concentration of the C l_{2}$ (4) $doing all of these.$ 195. $What is the activation energy for a reaction if its rate doubles when the temperature is raised from 2 0^{0} C to 3 5^{o} C ? (R = 8.314 J mol^{- 1} K^{- 1})$ (1) $34.7 k J m o l^{- 1}$ (2) $15.1 k J m o l^{- 1}$ (3) $342 k J m o l^{- 1}$ (4) $269 k J m o l^{- 1}$ 196. $For the reaction; 2 N_{2} O_{5} \to 4 N O_{2} + O_{2} rate and rate constant are 1. 02 \times 1 0^{- 4} and 3. 4 \times 1 0^{- 5} se c^{- 1} respectively, then concentration of N_{2} O_{5} at that time will be$ (1) $1.732$ (2) $3$ (3) $1.02 \times 1 0^{- 4}$ (4) $3.4 \times 1 0^{5}$ 197. $The rate of a first order reaction is 1.5 \times 1 0^{- 2} mol L^{- 1} mi n^{- 1} at 0.5 M concentration of the reactant. The half‐life of the reaction is$ (1) $0.383 min$ (2) $23.1 min$ (3) $8.73 min$ (4) $7.53 min$ 198. $For zero order reaction, a plot of t_{1/2} versus [A]_{0} will be$ (1) $a straight line passing through the origin and slope = k$ (2) $a horizontal line (parallel to x -axis)$ (3) $a straight line with slope - k$ (4) $a straight line passing through origin and slope = \frac{1}{2 k}$ 199. $The activation energy of a reaction can be determined from the slope of which of the following graphs?$ (1) $l n k v s \frac{1}{T}$ (2) $\frac{T}{l n k} v s \frac{1}{T}$ (3) $l n k v s T$ (4) $\frac{l n k}{T} v s T$ 200. $Reactant A converts to product D through the given mechanism (with the net evolution of heat): A \to B slow; Δ H = + ve B \to C fast; Δ H = - ve C \to D fast; Δ H = - ve Which of the following represents the above reaction mechanism?$ (1) (2) (3) (4) 201. $r = k [A] for a reaction, 50 % of A is decomposed in 120 minutes. The time taken for 90 % decomposition of A is______ minutes.$ 202. $The ratio of^{14} C in a piece of wood is \frac{1}{8} part that of atmosphere. If half life of^{14} C is 5730 years, the age of wood sample is______ years.$ 203. $Time required for 99.9 % completion of a first order reaction is______times the time required for completion of 90 % reaction.(nearest integer)$ 204. $A molecule undergoes two independent first order reactions whose respective half lives are 12 min and 3 min. If both the reactions are occurring then the time taken for the 50% consumption of the reactant is min. (Nearest integer)$ 205. $For the given first order reaction A \to B the half life of the reaction is 0.3010 min. The ratio of the initial concentration of reactant to the concentration of reactant at time 2.0 min will be equal to___________. (Nearest integer)$ 206. $A first order reaction has the rate constant, k = 4.6 x 1 0^{- 3} s^{- 1} . The number of correct statement/s from the following is/are________. Given : log 3 = 0.48 A. Reaction completes in 1000 s. B. The reaction has a half-life of 500 s. C. The time required for 10% completion is 25 times the time required for 90% completion. D. The degree of dissociation is equal to (1 - e^{- k t}). E. The rate and the rate constant have the same unit.$ 207. $A flask is filled with equal moles of A and B. The half lives of A and B are 100 s and 50 s respectively and are independent of the initial concentration. The time required for the concentration of A to be four times that of B is _________ (Given : ln 2 = 0.693)$ 208. $The reaction between X and Y is first order with respect to X and zero order with respect to Y. Experiment \frac{[ ^{X} ]}{m o l L ^{- 1}} \frac{I ni t ia l r a t e}{m o l L ^{- 1} mi n ^{- 1}} I. 0.1 0.1 2 x 1 0^{- 3} II. L 0.2 4 x 1 0^{- 3} III. 0.4 0.4 M x 1 0^{- 3} IV. 0.1 0.2 2 x 1 0^{- 3} Examine the data of table and calculate ratio of numerical values of M and L. (Nearest Inetger)$ 209. $The reaction that occurs in a breath analyser, a device used to determine the alcohol level in a person's blood stream is 2 K_{2} C r_{2} O_{7} + 8 H_{2} S O_{4} + 3 C_{2} H_{6} O \to 2 C r_{2} (S O_{4})_{3} + 3 C_{2} H_{4} O_{2} + 2 K_{2} S O_{4} + 11 H_{2} O If the rate of appearance of C r_{2} (S O_{4})_{3} is 2.67 mol mi n^{- 1} at a particular time, the rate of disappearance of C_{2} H_{6} Oat the same time is ____ mol mi n^{- 1} . (Nearest integer)$ 210. $The half life for the decomposition of gaseous compound A is 240 s when the gaseous pressure was 500 Torr initially. When the pressure was 250 Torr, the half life was found to be 4.0 min. The order of the reaction is.......(Nearest integer)$