Question

18. From the reaction data below, determine whether the reaction is first-order or second-order. Time (S) Reactant (M) 6.67 1.59 0.74 0.39 0.16 25 a. First-order. b. Second-order. c. Zero-order. d. Cannot determine. 19. In the Question 18, what is the rate constant for the reaction? a. 0.12 b. 0.15 c. 0.24 d. 0.72 20. In the Question 18, what is the half-life for the reaction? a. 0.2 sec b. 0.6 sec c. 1.0 sec d. 1.3 sec

Answer 1

soln (18) for lit interval - t = (2-0) - 28ec. concentrate on [A [A ] = 6.67 ] = 1.59 for first order reaction Kt= 2.303 kt = 2.303 x dog [A] kx2 = 2.303 x log 16:65 J IK = 0.717 5' / for and interval t = 15-2) = 3 sec. [At] = 0.74 [A] = 1.59 for first order reaction. kxt = 2. 3037 kx3 = 2.303 x log [ Use you] KX 3 = 2.303 X 니 K = 0.255 5-1 for the different not equal , so reaction. time this intervals is not rate a constant is. first order. Now, check for second order reaction -

for second for first I CA] t = (2-0 =2) sec. order reaction, time interval - kt & I [AJ kx2 + 1 1.59 6.67 [K = 0.24 M's for and time interval t = (5-2 =3 sec., H = 0.74 A = 1.59 I - kt + 1 [A4] [A] KX 3 + 1 0.74 1.59 - K = 0.240 M's A o since intervals , so reaction. option rate the constant is reaction same is a for two time second order (b) is correct answer sol 1 As constant rate is calculated the ques value (18) of the , so in rate constant k = 0.24 M's i option (c) is the correct answer.

20 for the second order reaction, half-time t1/2 = t1/2 K[A 2 [:[.] = 6,67] 0.24 x 6.67 1.6008 0.6 sec. Answer