Chemical Kinetics PYQs Set 6 (PDF)

Set 6 of 11 · Questions 151-180 of 311

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Chemical Kinetics · Set 6 (Q151-180)
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151. $In a reaction A + B \to C, initial concentrations of A and B are related as [A]_{0} = 8 [B]_{0} . The half lives of A and B are 10 min and 40 min, respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?$ (1) $20 min$ (2) $40 min$ (3) $80 min$ (4) $60 min$ 152. $For a chemical reaction, mA \to xB, the rate law is r = k [A]^{2} . If the concentration of A is doubled, the reaction rate will be$ (1) $doubled$ (2) $quadrupled$ (3) $increased by 8 times$ (4) $unchanged.$ 153. $The rate constant of a reaction is given by k = PZ e^{- E_{a} / RT} under standard notation. In order to speed up the reaction, which of the following factors has to be decreased?$ (1) $Both Z and T$ (2) $E_{a}$ (3) $T$ (4) $Z$ 154. $For the reaction, A_{2} + B + C \to AC + AB, it is found that tripling the concentration of A_{2} triples the rate, doubling the concentration of C doubles the rate and doubling the concentration of B has no effect. What is the rate law?$ (1) $k (A_{2})^{2} [C]$ (2) $k [B]^{1/2} [C]$ (3) $k (A_{2}) [C]$ (4) $k (A_{2})^{3} [B]^{2} [C]$ 155. $A possible mechanism for the gaseous reaction 2 H_{2} + 2 NO \to 2 H_{2} O + N_{2} is Step 1: 2 NO ⇌ N_{2} O_{2} Step 2: N_{2} O_{2} + H_{2} \to N_{2} O + H_{2} O (slow) Step 3: N_{2} O + H_{2} \to N_{2} + H_{2} O The rate law for this :eaction is$ (1) $R = k [NO]^{2} (H_{2})^{2}$ (2) $R = k [NO] (H_{2})^{2}$ (3) $R = k [NO]^{1/2} (H_{2})$ (4) $R = k [NO]^{2} (H_{2})$ 156. $The following results were obtained during kinetic studies of the reaction; 2 A + B \to Products Experiment [A] (in mol L^{- 1}) [B] (in mol L^{- 1}) Initial Rate of reaction (in mol L^{- 1} min^{- 1}) I 0.10 0.20 6.93 \times 10^{- 3} II 0.10 0.25 6.93 \times 10^{- 3} III 0.20 0.30 1.386 \times 10^{- 2} The time (in minutes) required to consume half of A is :$ (1) $5$ (2) $10$ (3) $1$ (4) $100$ 157. $What is the concentration (in mol L^{- 1}) of the product after 20 s in the following reaction. Given that A \to 3 B, rate = k [A]^{\circ} Time(s) Concentration of the reactant (mol L^{- 1}) 0 0.1 15 0.05 20 0.1 - x$ (1) $6.6 \times 10^{- 2}$ (2) $1.32 \times 10^{- 1}$ (3) $1.98 \times 10^{- 1}$ (4) $2.2 \times 10^{- 2}$ 158. $Rate constants in the following reaction are Reaction 1: A \to catalyst 1 P_{1}, k_{1} = 1 s^{- 1} Reaction 2 : A \to catalyst 2 P_{2}, k_{2} = 0.1 L mol^{- 1} s^{- 1} Reaction 3 : A \to catalyst 3 P_{3}, k_{3} = 0.01 L^{2} mol^{- 2} s^{- 1} The correct relations between the rate of the reactions at 1 M of A are$ (1) $r_{1} = \frac{r _{3}}{100}, r_{2} = \frac{r _{3}}{10}$ (2) $r_{1} = \frac{r _{2}}{10}, r_{2} = \frac{r _{3}}{10}$ (3) $r_{1} = 100 r_{3}, r_{2} = \frac{r _{3}}{10}$ (4) $r_{1} = 10 r_{2}, r_{3} = \frac{r _{2}}{10}$ 159. $Calculate the rate constant of the first order reaction if 80 % of the reactant decomposes in 60 minutes.$ (1) $2.68 \times 10^{- 2} minute^{- 1}$ (2) $5.36 \times 10^{- 2} minute^{- 1}$ (3) $1.34 \times 10^{- 2} minute^{- 1}$ (4) $8.1 \times 10^{- 2} minute^{- 1}$ 160. $Temperature coefficient of a reaction is ' 2 '. When temperature is increased from 30^{\circ} C to 90^{\circ} C, the rate of reaction is increased by$ (1) $60 times$ (2) $64 times$ (3) $150 times$ (4) $400 times.$ 161. $The decomposition of phosphine (_{3}^{P H}) on tungsten at low pressure is a first‐order reaction. It is because the$ (1) $rate is proportional to the surface coverage$ (2) $rate is inversely proportional to the surface coverage$ (3) $rate is independent of the surface coverage$ (4) $rate of decomposition is very slow.$ 162. $Chemical reactions with very high E_{a} values are generally$ (1) $very fast$ (2) $very slow$ (3) $moderately fast$ (4) $spontaneous.$ 163. $For the decomposition of a compound AB at 600 K, the following data were obtained [AB] mol dm^{- 3} Rate of decomposition of AB in mol dm 0.20 2.75 \times 10^{- 8} 0.40 11.0 \times 10^{- 8} 0.60 24.75 \times 10^{- 8} The order for the decomposition of AB is$ (1) $0$ (2) $1$ (3) $2$ (4) $1.5$ 164. $If the following reaction : xA \to yB = log_{10} (- \frac{d ( A )}{dt}) = log_{10} (\frac{d ( B )}{dt}) + 0.3010 ‘A’ and ‘B’ respectively can be:$ (1) $n - Butane and Iso-butane$ (2) $C_{2} H_{2} and C_{6} H_{6}$ (3) $C_{2} H_{4} and C_{4} H_{8}$ (4) $N_{2} O_{4} and N O_{2}$ 165. $Rate law for the reaction, A + B \to product is rate = k ((A)^{2} [B]) . What is the rate constant, if rate of reaction at a given temperature is 0.22 M s^{- 1}, when [A] = 1 M and [B] = 0.25 M ?$ (1) $3.52 M^{- 2} s^{- 1}$ (2) $1.136 M^{- 2} s^{- 1}$ (3) $0.88 M^{- 2} s^{- 1}$ (4) $0.05 M^{- 2} s^{- 1}$ 166. $The rate constant, k of a zero order reaction 2 NH_{3} (g) \to Pt 1130 k N_{2} (g) + 3 H_{2} (g) is y \times 10^{- 4} mol L^{- 1} s^{- 1} . The rate of formation of hydrogen (in mol L^{- 1} s^{- 1}) is$ (1) $y \times 10^{- 4}$ (2) $2y\times 1 0^{- 4}$ (3) $3y\times 1 0^{- 4}$ (4) $y3\times 1 0^{- 4}$ 167. $For the reaction, 2 SO_{2} + O_{2} ⇌ 2 SO_{3}, the rate of disappearance of O_{2} is 2 \times 10^{- 4} mol L^{- 1} s^{- 1} . The rate of appearance of SO_{3} is$ (1) $2 \times 10^{- 4} mol L^{- 1} s^{- 1}$ (2) $4 \times 10^{- 4} mol L^{- 1} s^{- 1}$ (3) $1 \times 10^{- 1} mol L^{- 1} s^{- 1}$ (4) $6 \times 10^{- 4} mol L^{- 1} s^{- 1}$ 168. $The graph obtained between ln k (k = Rate constant) on y -axis 1/ T on x -axis is a straight line. The slope of it is - 4 \times 10^{4} k . The activation energy of the reaction (in kJ mol^{- 1})is (R = 8.3 J K^{- 1} mol^{- 1})$ (1) $166$ (2) $332$ (3) $765$ (4) $382$ 169. $The activation energy for a simple chemical reaction A ⇌ B is E_{a} in forward direction. The activation energy for reverse reaction$ (1) $is negative of E_{a}$ (2) $is always less than E_{a}$ (3) $can be less than or more than E_{a}$ (4) $is always double of E_{a} .$ 170. $For a reaction, A + B \to Products, the rate of the reaction at various concentrations are given below : Expt No [A] [B] rate (mol dm^{- 3} s^{- 1}) 1 0.2 0.2 22 0.2 0.4 43 0.6 0.4 36 The rate law for the above reaction is$ (1) $r = k [A]^{2} [B]$ (2) $r = k [A]^{3} [B]$ (3) $r = k [A] [B]^{2}$ (4) $r = k [A]^{2} [B]^{2}$ 171. $When the temperature of a reaction is raised by 10^{\circ} C, how many times the rate will be enhanced?$ (1) $1.5$ (2) $3$ (3) $2$ (4) $4$ 172. $In the reaction, A \to products, If the concentration of the reactant is doubled rate of the reaction remains unchanged. The order of the reaction with respect to A is$ (1) $1$ (2) $2$ (3) $0.5$ (4) $0$ 173. $The rate of chemical reaction doubles with every 10^{\circ} C rise in temperature. If the reaction is carried out in the vicinity of 22^{\circ} C, the activation energy of the reaction is (given R = 8.3 J K^{- 1} mol^{- 1}, ln 2 = 0.69 and ln 3 = 1.1)$ (1) $1.69 kJ mol^{- 1}$ (2) $0.169 kJ mol^{- 1}$ (3) $49.8 kJ mol^{- 1}$ (4) $498 J mol^{- 1}$ 174. $N O_{2} required for a reaction is produced by the decomposition of N_{2} O_{5} in CC l_{4} as per the equation, 2 N_{2} O_{5} (g) \to 4 N O_{2} (g) + O_{2} (g) . The initial concentration of N_{2} O_{5} is 3.00 mol L^{- 1} and it is 2.75 mol L^{- 1} after 30 minutes. The rate of formation of N O_{2} is :$ (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) $2.083 \times 10^{- 3} mol L^{- 1} min^{- 1}$ 175. $The rate constant of a reaction is increased 4 times after addition of catalyst to the reaction mixture at the same temperature of 27^{\circ} C . The change in the activation energy of this reaction is (Take ln (\frac{1}{4}) = - 1.386, R = 8.314)$ (1) $- 15 kJ / mol$ (2) $- 1.5 kJ / mol$ (3) $- 3.45 kJ / mol$ (4) $- 34.5 kJ / mol$ 176. $Thermal decomposition of HCOOH is a first order reaction and the rate constant at T (K) is 4.606 \times 10^{- 3} s^{- 1} . The time required to decompose 90 % of initial quantity of HCOOH at T (K) in second is$ (1) $100$ (2) $500$ (3) $1000$ (4) $50$ 177. $For a reaction A \to K 1 B \to K 2 C If the rate of formation of B is set to be zero then the concentration of B is given by :$ (1) $(K_{1} + K_{2}) [A]$ (2) $(K_{1} / K_{2}) [A]$ (3) $(K_{1} - K_{2}) [A]$ (4) $K_{1} K_{2} [A]$ 178. $An exothermic reaction X \to Y has an activation energy 30 kJmol^{- 1} . If energy change ∆ E during thereaction is - 20 kJ, then the activation energy for the reverse reaction in kJ is -$ 179. $Time required for completion of 99.9 % of a First order reaction is______ times of half life (t_{1/2}) of the reaction.$ 180. $The rate of a reaction decreased by 3.555 times when the temperature was changed from 40^{\circ} C to 30^{\circ} C . The activation energy (in kJmol^{- 1}) of the reaction is ⟶ take; R = 8.314 Jmot^{- 1} K^{- 1} ln 3.555 = 1.268$