Questions 18-21 use the information below. Consider the hypothetical reaction represented by the balanced equation below with its experimental rate Jaw. Data from the first kinetic trial of this reaction is also shown in the table. Note that the results of the first kinetic trial show the initial rate of formation of product c. (AC) for the initial concentrations of reactants A and B of 6.0 Mand 2.0 M, respectively. 2 A(g) +B(g) 2 Cig) Rate =[AB] AI Trial [A], (M) (BI,(M(1992) , cat ses [C] A1 6.0 2.0 +0.72 At the beginning of one trial of this reaction. [A] - 6.0 Mand [B] - 2.0 M. The observed rate for the formation or for this trial is 0.72 mol Losec ! 18. Determine the [A] when [B] drops to 0.50 M. (A) 3.0 M (B) 2.0 M (C) 1.5 M (D) 1.0M 19. What is the rate of disappearance of reactant B for this trial? (A) 0.36 mol L-isce- (B) 0.72 mol L-'sec (C) 1.4 mol L-see- (D) 2.8 mol L-sec 20. What are the units for k, the rate constant for this experiment? (A) M sec (B) sec (C) Msec (D) M?sec 1 CHAPTER 9 21. Which statement below describes how the rate for this trial, at constant temperature, changes as [B] approaches 0.5 M? (A) The rate remains the same because the rate constant remains the same. (B) The rate remains the same because the temperature remains the same. (C) The rate decreases because the concentrations of A and B are decreasing. (D) The rate decreases because the activation energy decreases