Unit9 Chemical kinetics qns

# Unit9 Chemical kinetics qns - 1 UNIT 9 CHEMICAL KINETICS 1...

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1 QUEST TUTORIALS Head Office : E-16/289, Sector-8, Rohini, New Delhi, Ph. 65395439 UNIT 9 CHEMICAL KINETICS 1. The rate law for a reaction A + B products, is rate = k [A] 1 [B] 2 . Then, which one of the following statements is false ? (a) If [B] is held constant while [A] is doubled, the reaction will proceed twice as fast. (b) If [A] is held constant while [B] is reduced to one quarter, the rate will be halved (c) If [A] and [B] are both doubled, the reaction will proceed 8 times as fast. 2. Fro a first order reaction, a straight line is obtained if you plot (a) log Conc Vs time (b) Conc. Vs time (c) Conc 1 Vs time (d) log Conc Vs Conc 1 3. For a given first order reaction, it takes 20 minutes for the reaction to drop from 1.0 M to 0.60 M. The time required for the concentration to drop from 0.60 M to 0.36 M will be (a) more than 20 minutes (b) 20 minutes (c) less than 20 minutes (d) none of these 4. For a certain decomposition, the rate is 0.30 M sec –1 when the concentration of reactant is 0.20 M. If the reaction is second order, the rate (in M sec –1 ) when concentration is increased 3-fold is (a) 0.30 (b) 0.90 (c) 0.60 (d) 2.70 5. A 10º rise in temperature doubles the rate of reaction. This is because more molecules obtain (a) activation energy (b) a catalyst (c) a new reaction path (d) the rate-determining step 6. The unit for rate constant of a zero order reaction is (a) sec –1 (b) 1 mole –1 sec –1 (c) mole 1 –1 sec –1 (d) dimensionless 7. For a given reaction, the rate constant at 37ºC is twice that at 27ºC, its energy of activation in Joules is computed at (a) log 2 1 = 31 . 8 303 . 2 Ea × × 310 300 10 (b) log 2 1 = 31 . 8 303 . 2 Ea × × 310 300 10 (c) log 2 1 = 31 . 8 303 . 2 Ea × × 37 27 10 × (d) 1 2 = 31 . 8 303 . 2 Ea × 310 300 10 × 8. In arrhenius equation, the fraction of effective collisions is given by (a) k =A e –Ea/RT (b) A (c) e –Ea/RT (d) none of these 9. Quantum yield of a photochemical reaction is given by (a) absorbed quanta of number reacting molecules of number (b) absorbed einsteins reacting moles (c) both of these (d) none of these 10. For a first order reaction A products, the concentration of [A] is reduced from 1 M to 0.125 M in one hour, the t 1/2 of this reaction (in sec) is (a) 600 (b) 300 (c) 1200 (d) 1200 693 . 0 11. For the reaction 2N 2 O 5 2N 2 O 4 + O 2 , the rate law equation is rate = k [N 2 O 5 ]. The half life for the process at 25ºC and 55ºC for the process are respectively 1.69 × 10 4 sec. And 330 seconds. The energy of activation for the reaction in K.cals is (a) 26 (b) 13 (c) 52 (d) none of these 12. For the reaction 2NO (g) + Cl 2 (g) 2NOCl (g)

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2 QUEST TUTORIALS Head Office : E-16/289, Sector-8, Rohini, New Delhi, Ph. 65395439 [NO] [Cl 2 ] Initial rate moles per moles per moles litre litre l –1 sec –1 0.10 0.10 1 0.20 0.20 8 0.10 0.20 2 (a) rate = k[NO] 2 [Cl 2 ] 1 (b) rate = k[NO] 1 [Cl 2 ] 1 (c) rate = k[NO]
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Unit9 Chemical kinetics qns - 1 UNIT 9 CHEMICAL KINETICS 1...

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