Exp. [A] mol/l [B] mol/l rate of formation of C (M/min)

Transcription

1 1. The following rate data were obtained at 25 C for the indicated reaction. What is the rate-law expression for the reaction A + B 6 C? Exp. [A] mol/l [B] mol/l rate of formation of C (M/min) x x x x 10-4 a) rate = k[a] [B] b) rate = k[a] [B] 2 c) rate = k[a] 2 [B] d) rate = k[a] 2 [B] 2 e) rate = k[a] 2. The balanced equation for the reaction of bromate ion with bromide in acidic solution is given by: BrO Br H Br H 2 O At a particular instant in time, the value of -)[Br - ]/)t is 2.0 x 10-3 mol/l s. What is the value of )[Br 2 ]/)t in the same units? a) 1.2 x 10-3 b) 6.0 x 10-3 c) 3.3 x 10-3 d) 3.3 x 10-5 e) 2.0 x For the reaction 2 NO 2 (g) 6 2 NO(g) + O 2 (g), a graph of ln [NO 2 ] versus time is a straight line with a slope of s -1 at 40 o C. From this we can conclude: a) rate = k [NO 2 ] 2 and k = 1.29 M -1 s -1. b) rate = k [NO 2 ] 2 and k = M -1 s -1. c) rate = k [NO 2 ] and k = s -1. d) rate = k [NO 2 ] and k = s -1. e) E a = 64.4 kj/mol. 4. Given k = 6.2 x 10-3 s -1 for a reaction which is first order in A, what is the initial rate of the reaction (M/s) when the initial concentration of A is M. a) 9.0 x 10-5 b) 6.2 x 10-5 c) 3.1 x 10-5 d) 1.2 e) 1.2 x 10 1

2 5. (7 pts) The initial rate of a reaction which is second order in A is 4.9 x 10-4 M/sec when the initial concentration is M. What is the second order rate constant (M -1 sec -1 )? a) 5.4 x 10 1 b) 6.8 x 10 1 c) 8.4 x 10 1 d) 6.8 x 10 2 e) 8.4 x (7 pts) The rate constant of a first order reaction is 3.86 x 10-3 s -1. What concentration of reactant will remain after 74.4 sec for an initial concentration of M? a) b) c) d) e) For the reaction A 6 Products, successive half-lives are observed to be 10.0 min, 20.0 min, and 40.0 min. At the beginning of the reaction, [A] was 0.10 M. The numerical value of the rate constant (M -1 min -1 ) is a) b) 1.0 c) 10.0 d) 5.0 x 10-3 e) none of these 8. The half life of a first order reaction is 45.6 sec. What is the first order rate constant (sec -1 )? a) 6.56 x 10-3 b) 9.10 x 10-3 c) 1.25 x 10-2 d) 1.52 x 10-2 e) 2.25 x What is the half life in sec for a second order reaction in reactant A with the rate constant k = 2.74 x 10-1 M -1 s -1 if the initial concentration is M? a) 8.59 b) 9.63 c) 12.2 d) 14.1 e) Ozone is believed to decompose according to the following mechanism. What would be the rate expression if the mechanism is correct? 2 O O 2 (balanced equation) O 3 W O 2 + O O 3 + O 6 2 O 2 (fast) (slow) a) rate = k [O 3 ] 2 b) rate = k [O 3 ] 2 /[O 2 ] c) rate = k [O 3 ] 2 [O] d) rate = k [O 2 ]

3 e) rate = k [O 2 ] (7 pts) Consider the following hypothetical reaction and the established rate law. Select an acceptable mechanism. A 2 + B 2 6 X + Y rate = k [A 2 ] [B 2 ][X] -1 a) A 2 W 2 A (fast) b) A 2 W C + X (fast) B 2 + A 6 C (slow) B 2 + C 6 Y (slow) C + A 6 X + Y (fast) c) A 2 + B 2 W C (fast) d) B B (slow) C 6 X + Y (slow) B + A 2 6 C (fast) C + B 6 X + Y (fast) e) B 2 W 2 B (fast) B 6 C + X (slow) C 6 Y (fast) 12. The enthalpy of activation of a first order reaction is 105 kj/mole. The rate constant at 45 C is 3.54 x 10-5 s -1. What is the rate constant (s -1 ) at 60 C? (R = 8.31 J/mole K). a) 4.24 x 10-5 b) 6.75 x 10-5 c) 1.02 x 10-4 d) 1.50 x 10-4 e) 2.12 x Which of the following statements is false about a catalyst? a) a catalyst does not change the equilibrium constant for a reaction b) a catalyst lowers the activation energy of a reaction c) a catalyst does not undergo any net chemical change d) a catalyst increases the kinetic energy of the reactants e) a catalyst in living systems are called enzymes 14. Given [CO] = M, [H 2 ] = M, [CH 4 ] = M and [H 2 O] = M for the following reaction at 1200 K calculate the equilibrium constant. 3 H 2 (g) + CO(g) W CH 4 (g) + H 2 O(g)

4 a) 3.92 b) 4.68 c) 5.04 d) 5.94 e) The equilibrium constant for the following reaction is 0.28 at 900 C. A system at equilibrium has [CS 2 ] = M, [H 2 ] = and [CH 4 ] = 8.40 x 10-5 M. What is the [H 2 S]? CS 2 (g) + 4 H 2 (g) W CH 4 (g) + 2 H 2 S(g) a) 0.11 b) 0.15 c) 0.20 d) 0.27 e) ( 7 pts) At 700 K, a 2.0-L flask initially contains 1.00 mol NO and 1.0 mol Cl 2 which react according to the equation 2 NO(g) + Cl 2 (g) W 2 NOCl(g). When the system comes to equilibrium, 0.32 mol of NO is present. Calculate the equilibrium constant K c at this temperature. a) 0.22 b) 8.0 c) 14 d) 21 e) (9 pts!!!) The following reaction has a K c = If a M solution of PCl 5 is placed in the reactor and allowed to reach equilibrium, what is the equilibrium concentration of PCl 3? a) M b) M c) M d) M e) M PCl 5 (aq) W Cl 2 (aq) + PCl 3 (aq) 18. The K c for the following reaction at 940 C is Given the concentrations [CO 2 ] = M, [H 2 ] = M, [CO] = M and [H 2 O] = M, one can conclude that

5 H 2 (g) + CO 2 (g) W CO(g) + H 2 O(g) a) the system is not at equilibrium and the reaction will proceed to the right b) the system is not at equilibrium and the reaction will proceed to the left c) the system is at equilibrium and no net change will occur 19. Choose from the following equilibrium systems I. 2 OF 2 (g) W 2 F 2 (g) + O 2 (g) K c = 7.3 x II. Br 2 (g) + Cl 2 (g) W 2 BrCl(g) K c = 6.3 III. C(s) + H 2 O(g) W CO(g) + H2(g) K c = 0.16 IV. NH 4 HS(s) W NH 3 (g) + H 2 S(g) K p = 9.4 x 10-2 the reaction which most favors products is and the reaction for which K p = K c is. a) IV, II b) III, IV c) II, III d) I, II e) I, III 20. Consider the following reactions. In which cases is product formation favored by increased pressure? 1) N 2 (g) + 3 H 2 (g) W 2 NH 3 (g) )H = kj 2) 2 CO 2 (g) W 2 CO(g) + O 2 (g) )H = 566 kj 3) CO(g) + 2H 2 (g) W CH 3 OH(R) )H = kj 4) N 2 (g) + O 2 (g) W 2 NO(g) )H = 181 kj 5) H 2 (g) + F 2 (g) W 2 HF(g) )H = -541 kj a) 2, 4 b) 1, 3 c) 2, 5 d) 4, 5 e) Consider the following reactions at equilibrium and determine which of the indicated changes will cause the reaction to proceed to the right. 1) CO(g) + 3 H 2 (g) W CH 4 (g) + H 2 O(g) (remove H 2 O) 2) N 2 (g) + 3 H 2 (g) W 2 NH 3 (g) (add NH 3 )

6 3) H 2 (g) + F 2 (g) W 2 HF(g) (add HF) 4) N 2 (g) + 2 O 2 (g) W 2 NO 2 (g) (remove NO 2 ) 5) BaO(s) + SO 3 (g) W BaSO 4 (s) (add BaO) a) 1, 4, 5 b) 1, 4 c) 2, 3 d) 2, 3, 5 e) 3, For the following reaction, which condition will shift the equilibrium to the right? 4 HCl(g) + O 2 (g) W 2 H 2 O(g) + 2 Cl 2 (g) + heat a) adding a catalyst b) adding more water c) decreasing the pressure d) decreasing the temperature e) more than one of the above is correct 23. Assume that the following reaction has come to equilibrium. If now the pressure is increased, one would predict that 2 NO 2 W N 2 O 4 a) the system will react to increase the concentration of N 2 O 4 b) the system will react to increase the concentration of NO 2 c) the amounts of both reactant and product will remain unchanged but the both the forward and reverse reactions will be accelerated d) the amounts of both reactant and product will remain unchanged but the both the forward and reverse reactions will be slowed e) a prediction cannot be made without knowing whether the reaction is exothermic or endothermic 24. The equilibrium constant K c for the following reaction at 800 C is 7.14 x What is K p at this temperature? 2 CO(g) W C(s) + CO 2 a) 7.14 x 10-2 b) 8.11 x 10-4 c) 5.92 x 10 2 d) 6.29 e) 9.22 x What is the conjugate acid of H 2 PO 4 -? a) H 3 PO 4 b) H 2 PO 4 c) H 2 PO 4 + d) HPO 4 2- e) HPO 4 -

7 26. Hydrazine (N 2 H 4 ), formerly used as a rocket fuel, is a base. What is its conjugate acid a) N 2 H 5 b) N 2 H 5 + c) N 2 H 5 - d) N 2 H 3 + e) N 2 H Some lemon juice has a hydrogen ion concentration of 5.0 x 10-3 M. What is the ph of the lemon juice? a) 3.30 b) 2.70 c) 2.30 d) 1.70 e) The hydroxide ion concentration of a wine is 7.1 x M. What is the ph of the wine? a) 2.85 b) 3.85 c) 2.15 d) 3.15 e) Some Useful information gas constant R = L-atm/mol-K = J/mol-K for water at 25 o C K w = 1.00 x Arrhenius equation, ln k ln A E a = RT

8 2 The quadratic equation ax + bx + c = 0 has the solutions b b ac x = ± 4 2a 2