CHAPTER CHEMICAL KINETICS

Transcription

1 161 CHAPTER CHEMICAL KINETICS 1. volume force pressure conc. of reactants Ans: 6. In a reversible reaction the energy of activation of the forward reaction is 50 kcal. The energy of activation for the reverse reaction will be [1996] < 50 kcal either greater than or less than 50 kcal 50 kcal > 50 kcal [1994] rate = k [B] 3 rate = k [B] 4 rate = k [A] [B] 3 rate = k [A] 2 [B] 2 Ans: 2. For an exothermic reaction, the energy of activation of the reactants is [1994] equal to the energy of activation of products less than the energy of activation of products greater than the energy of activation of products Sometimes greater and sometimes less than that of the products 3. Achemical reaction is catalyzed by a catalyst X. Hence X [1995] reduces enthalpy of the reaction decreases rate constant of the reaction increases activation energy of the reaction does not affect equilibrium constant of the reaction Ans: 4. Asubstance 'A' decomposes by a first order reaction starting initially with [A] = 2.00 m and after 200 min, [A] becomes 0.15 m. For this reaction t1/2 is [1995] min min min min Ans: 5. The rate of reaction depends upon the [1995] 7. The plot of concentration of the reactant vs. time for a reaction is a straight line with a negative slope. The reaction follows a [1996] zero order rate equation first order rate equation second order rate equation third order rate equation 8. Activation energy of a chemical reaction can be determined by [1998] evaluating rate constant at standard temperature evaluating velocities of reaction at two different temperatures evaluating rate constants at two different temperatures changing concentration of reactants Ans: 9. Half life of a first order reaction is 4 s and the initial concentration of the reactants is 0.12 M. The concentration of the reactant left after 16 s is [1999] M 0.06 M 0.03 M M Ans: 10. [2000]

2 162 Ans: 11. When a biochemical reaction is carried out in laboratory in the absence of enzyme then rate of reaction obtained is 10 6 times, then activation energy of reaction in the presence of enzyme is [2001] 6/RT Different from Ea obtained in laboratory Pis required Can't say anything 12. [2002] the rate of reaction is proportional to square of concentration of A the rate of reaction remains same at any concentration of A the rate remains unchanged at any concentration of Band C the rate of reaction doubles if concentration of Bis increased to double 15. [2003] [2001] 1.732M 3M M M 13. [2002] Ans: 16. If the rate of the reaction is equal to the rate constant, the order of the reaction is [2003] [2003] Is always double of Ea Is negative of Ea Is always less than Ea Can be less than or more than Ea Ans: 18.

3 163 [2003] 2 hours 1 hour 0.5 hour 0.25 hour 19. The rate of a first order reaction is mol L 1 min 1 at 0.5 Mconcentration of the reactant. The half life of the reaction is [2004] min 23.1 min 8.73 min 7.53 min 20. [2005] 30 s 220 s 300 s 347 s Ans: Ans: 23. [2006] Ans: The rate of reaction between two reactants Aand Bdecreases by a factor of 4 if the concentration of reactant Bis doubled. The order of this reaction with respect to reactant Bis: [2005] [2006] [2007] Aand B both neither A nor B A only B only Ans:

4 In a first-order reaction A --> B, if k is rate constant and inital concentration of the reactant A is 0.5 M, then the half-life is [2007] Ans: 26. If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in aproximately (log 4 = 0.60, log 5 = 0.69) [2007] 45 minutes 60 minutes 40 minutes 50 minutes Ans: 27. [2008] Ans: 28. [2008] Ans: [2009] mol L 1 s mol L 1 s mol L 1 s mol L 1 s 1 Ans: 30. [2009] Ans: 31. Half life period of a first-order reaction is 1386 seconds. The specific rate constant of the reaction is: [2009] s s s s

5 165 Ans: 36. [2009] rate = k [A] [B] 2 rate = k [A] 2 [B] 2 rate = k [A] [B] rate = k [A] 2 [B] Ans: 33. [2010] mol L 1 s 1 and mol L 1s mol L 1 s 1 and mol L 1 s mol L 1 s 1 and mol L 1 s mol L 1 s 1 and mol L 1 s 1 [2010] increasing the concentration of NO. increasing the temperature. increasing the concentration of the Cl2 doing all of these 37. Which one of the following statements for the order of a reaction is incorrect? [2011] Order can be determined only experimentally. Order is not influenced by stoichiometric coefficient of the reactants. Order of reaction is sum of power to the concentration terms of reactants to express the rate of reaction. Order of reaction is always whole number. Ans: 38. [2011] Ans: [2010] Ans: 35. [2010] [2011]

6 The unit of rate constant for a zero order reaction is [2011] mol L 1 s 1 L mol 1 s 1 L 2 mol 2 s 1 s 1 Ans: 41. [2012] Rate = k[a][b] 2 Rate = k[a] 2 [B] 2 Rate = k[a] [B] Rate = k[a] 2 B] Ans: 42. In a zero-order reaction for every 10 rise of temperature, the rate is doubled. If the temperature is increased from 10 C to 100 C, the rate of the reaction will become: [2012] 256 times 512 times 64 times 128 times 43. Activation energy (Ea) and rate constants (k1 and k2) of a chemical reaction at two different temperatures (T1 and T2) are related by: [2012] 44. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 C to 35 C? (R= Jmol 1 K 1 ) [2013] 269 kjmol kjmol kjmol kjmol A reaction having equal energies of activation for forward and reverse reaction has:[2013] 46. Areaction is 50% completed in 2 hours and 75% completed in 4 hours. The order of reaction is [2013] For a reaction between Aand B the order with respect to Ais 2 and the order with respect to B is 3. The concentrations of both Aand Bare doubled, the rate will increase by a factor of: [2013] Ans: 1. 2.

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