9. For the above reaction, determine the value of the rate constant and be sure
ID: 884198 • Letter: 9
Question
9. For the above reaction, determine the value of the rate constant and be sure to include units. Use the following data and first-order reaction information for questions 10-13. 11. What is the rate constant for this decomposition? time (sec) 12. What was the initial concentration of [A]? 13. What would the concentration be after 5.0 seconds? 10. What is the half-life for this reaction? The reaction A arrow products is first order. If the concentration of A decreases from 0.050 M to 0.025 M after 14 minutes, determine the rate constant of the reaction. 15. Determine the rate law based on the proposed mechanism below. Step 1 A + B leftrighttharpoons fast Step2 E+A arrow C+D slowExplanation / Answer
9.Reaction not provided.
Rate = -d[reactants] / dt
from given data, [A] = [A]FINAL - [A]INITIAL
= 0.61 - 0.86 = -0.25M
t = 6 - 3 = 3s
Rate = -(-0.25)/3 = 0.083333 mol lit-1sec-1
11. Since it firs order reaction, Rate = k [A]
Rate constant,k = 0.083333 / 0.61 = 0.1366 sec-1
12. k = (2.303/t) log [A0/A]
0.1366 = 2.303 / 3 ( log [A0] - log [A] )
log [A0] = 0.17794 + log 0.86 = 0.11244
[A0] = 1.2955 mol lit-1
13. k = (2.303/t) log [A0/A]
0.1366 = 2.303 / 5 (log 1.2955 - log A5sec)
A5sec = 0.6544 mol lit-1
10. For first order reaction t1/2 = 0.693 / k =0.693 /0.1366 = 5.073 sec
14. For first order reaction k = 0.693 / t1/2 = 0.693 /14 = 0.0495 min-1 (since initial conctration become half after 14min so t1/2 = 14min)
15. Since slow step is the rate determining step rate law is, Rate = k [E] [A]
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