Chemical Kinetics PYQs Set 6 (PDF)

Set 6 of 8 · Questions 151-180 of 224

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Mere Teacher · Previous Year Questions NEET Chemistry · Chemical Kinetics · Set 6 (Q151-180)
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151. $N O_{2} required for a reaction is produced by the decomposition of N_{2} O_{5} in CC l_{4} as per the equation, 2 N_{2} O_{5} (g) \to 4 N O_{2} (g) + O_{2} (g) . The initial concentration of N_{2} O_{5} is 3.00 mol L^{- 1} and it is 2.75 mol L^{- 1} after 30 minutes. The rate of formation of N O_{2} is :$ (1) $4.167 \times 10^{- 3} mol L^{- 1} min^{- 1}$ (2) $1.667 \times 10^{- 2} mol L^{- 1} min^{- 1}$ (3) $8.333 \times 10^{- 3} mol L^{- 1} min^{- 1}$ (4) $2.083 \times 10^{- 3} mol L^{- 1} min^{- 1}$ 152. $The rate constant of a reaction is increased 4 times after addition of catalyst to the reaction mixture at the same temperature of 27^{\circ} C . The change in the activation energy of this reaction is (Take ln (\frac{1}{4}) = - 1.386, R = 8.314)$ (1) $- 15 kJ / mol$ (2) $- 1.5 kJ / mol$ (3) $- 3.45 kJ / mol$ (4) $- 34.5 kJ / mol$ 153. $Thermal decomposition of HCOOH is a first order reaction and the rate constant at T (K) is 4.606 \times 10^{- 3} s^{- 1} . The time required to decompose 90 % of initial quantity of HCOOH at T (K) in second is$ (1) $100$ (2) $500$ (3) $1000$ (4) $50$ 154. $For a reaction A \to K 1 B \to K 2 C If the rate of formation of B is set to be zero then the concentration of B is given by :$ (1) $(K_{1} + K_{2}) [A]$ (2) $(K_{1} / K_{2}) [A]$ (3) $(K_{1} - K_{2}) [A]$ (4) $K_{1} K_{2} [A]$ 155. $If benzene diazonium chloride undergoes first order decomposition at T (K) with a rate constant of 6.93 \times 10^{- 2} min^{- 1}, the time for completion of 90 % of the reaction (in min) is (nearest integer) (log 2 = 0.30, log 3 = 0.477)$ (1) $15$ (2) $30$ (3) $33$ (4) $43$ 156. $A first order reaction has the rate constant of 1.15 \times 10^{- 3} s^{- 1} . The time required to reduce 10 g of reactant to 6 g is x \times 10^{2} sec . What is the approximate value of x ? (log 5 = 0.7, log 3 = 0.48)$ (1) $2.2$ (2) $3.3$ (3) $4.4$ (4) $1.1$ 157. $For the reaction 2 A + 3 B + \frac{3}{2} C \to 3 P which statement is correct?$ (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) $\frac{dn _{A}}{dt} = \frac{2}{3} \frac{dn _{B}}{dt} = \frac{3}{4} \frac{dn _{C}}{dt}$ 158. $A reaction, 3 X (g) \to 2 Y (g) + Z (g) takes place in a closed vessel. What is the rate of formation of Y (in mol L^{- 1}) if the rate of disappearance of X is 7.2 \times 10^{- 3} mol L^{- 1} s^{- 1} ?$ (1) $3.6 \times 10^{- 3}$ (2) $4.8 \times 10^{- 3}$ (3) $2.4 \times 10^{- 3}$ (4) $1.2 \times 10^{- 3}$ 159. $Which statement among the following is incorrect?$ (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) $Unit of rate constant k for a first order reaction is M s^{- 1} .$ 160. $Consider a gas phase reaction which occurs in a closed vessel 2 A \to 4 B + C The concentration of B is found to be increased by 5 \times 10^{- 3} mol L^{- 1} in 10 seconds. The rate of disappearance of A (in mol L^{- 1} s^{- 1}) is$ (1) $4.75 \times 10^{- 4}$ (2) $7.5 \times 10^{- 4}$ (3) $1.25 \times 10^{- 4}$ (4) $2.5 \times 10^{- 4}$ 161. $The reaction A_{2} + B_{2} \to 2 AB follows the mechanism A_{2} k_{1} k_{- 1} A + A (fast) A + B_{2} \to k_{2} AB + B (slow) AB + B \to AB (fast) The overall order of the reaction is:$ (1) $2$ (2) $2.5$ (3) $3$ (4) $1.5$ 162. $20 % of a first order reaction was found to be completed at 10:00 a.m at 11.30 a . m . on the same day, 20 % of the reaction was found to be remaining. The half life period in minutes of the reaction is$ (1) $90$ (2) $45$ (3) $60$ (4) $30$ 163. $In collision theory of chemical reaction, Z_{AB} represents$ (1) $The collision frequency of reactants, A and B$ (2) $Steric factor$ (3) $The fraction of molecules with energies equal to$ (4) $The fraction of molecules with energies greater than$ 164. $For a reaction A + 2 B \to Products, when concentration of B alone is increased, half life remains the same. If concentration of A alone is doubled, rate remains the same. The unit of rate constant for the reaction is$ (1) $s^{- 1}$ (2) $1.mol^{- 1} s^{- 1}$ (3) $molL-1 s^{- 1}$ (4) $atm^{- 1}$ 165. $An increase in the concentration of the reactants of a reaction leads to change in :$ (1) $Heat of reaction$ (2) $Threshold energy$ (3) $Collision frequency$ (4) $Activation energy$ 166. $For a zero order reaction, the plot of concentration of reactant vs time is (Hint: Consider the intercept on the concentration axis)$ (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) $linear with + ve slope and zero intercept$ 167. $Given above is the concentration vs time plot for a dissociation reaction: A \to nB . Based on the data of the initial phase of the reaction (initial 10 min), the value of n is____.$ (1) $3$ (2) $2$ (3) $4$ (4) $5$ 168. $The rate of the reaction, 2 N O + C l_{2} \to 2 N O C l is given by the rate equation rate = k [N O]^{2} [C l_{2}] . The value of the rate constant can be increased by$ (1) $increasing the temperature$ (2) $increasing the concentration of NO$ (3) $increasing the concentration of the C l_{2}$ (4) $doing all of these.$ 169. $What is the activation energy for a reaction if its rate doubles when the temperature is raised from 2 0^{0} C to 3 5^{o} C ? (R = 8.314 J mol^{- 1} K^{- 1})$ (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) $269 k J m o l^{- 1}$ 170. $For the reaction; 2 N_{2} O_{5} \to 4 N O_{2} + O_{2} rate and rate constant are 1. 02 \times 1 0^{- 4} and 3. 4 \times 1 0^{- 5} se c^{- 1} respectively, then concentration of N_{2} O_{5} at that time will be$ (1) $1.732$ (2) $3$ (3) $1.02 \times 1 0^{- 4}$ (4) $3.4 \times 1 0^{5}$ 171. $The rate of a first order reaction is 1.5 \times 1 0^{- 2} mol L^{- 1} mi n^{- 1} at 0.5 M concentration of the reactant. The half‐life of the reaction is$ (1) $0.383 min$ (2) $23.1 min$ (3) $8.73 min$ (4) $7.53 min$ 172. $For zero order reaction, a plot of t_{1/2} versus [A]_{0} will be$ (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) $a straight line passing through origin and slope = \frac{1}{2 k}$ 173. $The activation energy of a reaction can be determined from the slope of which of the following graphs?$ (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) $\frac{l n k}{T} v s T$ 174. $Reactant A converts to product D through the given mechanism (with the net evolution of heat): A \to B slow; Δ H = + ve B \to C fast; Δ H = - ve C \to D fast; Δ H = - ve Which of the following represents the above reaction mechanism?$ (1) (2) (3) (4) 175. $For a first‐order reaction, the half‐life period is independent of$ (1) $first power of final concentration$ (2) $cube root of initial concentration$ (3) $initial concentration$ (4) $square root of final concentration$ 176. $For the reaction H_{2 (g)} + I_{2 (g)} ⇌ 2 HI_{(g)}, the rate of reaction is expressed as$ (1) $\frac{Δ [ H _{2} ]}{Δ t} = \frac{1Δ [ I _{2} ]}{2Δ t} = - \frac{Δ [ H I ]}{Δ t}$ (2) $- \frac{Δ [ I _{2} ]}{Δ t} = - \frac{Δ [ H _{2} ]}{Δ t} = \frac{1Δ [ H I ]}{2Δ t}$ (3) $\frac{Δ [ I _{2} ]}{Δ t} = \frac{Δ [ H _{2} ]}{Δ t} = \frac{Δ [ H I ]}{2Δ t}$ (4) $none of these$ 177. $Consider the given plots for a reaction obeying Arrhenius equation (0° C < T < 300° C) : (K and E_{a} are rate constant and activation energy, respectively. Choose the correct option$ (1) $I is right but II is wrong$ (2) $Both I and II are correct$ (3) $I is wrong but II is right$ (4) $Both I and II are wrong$ 178. $Consider the following plots of rate constant versus \frac{1}{T} for four different reactions. Which of the following orders is correct for the activation energies of these reactions?$ (1) $E_{c} > E_{a} > E_{d} > E_{b}$ (2) $E_{a} > E_{d} > E_{c} < E_{b}$ (3) $E_{c} > E_{b} > E_{a} > E_{d}$ (4) $E_{d} > E_{a} > E_{b} > E_{c}$ 179. $Consider the following reactions A \to P 1; B \to P 2; C \to P 3; D \to P 4 The order of the above reactions are a, b, c and d, respectively. The following graph is obtained when log[rate] vs . log [conc.] are plotted Among the following, the correct sequence for the order of the reactions is$ (1) $d > b > a > c$ (2) $d > a > b > c$ (3) $a > b > c > d$ (4) $c > a > b > d$ 180. $The correct reaction profile diagram for a positive catalyst reaction.$ (1) (2) (3) (4)