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Chemistry LibreTexts

Kinetics Solutions

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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

1 Write the rate expression in terms of D[reactant]/Dt  and  D[product]/Dt:

  rate  = - D[N2]/Dt    =   - D[H2]/3Dt   =  D[NH3]/2Dt

2 Determine

  1. a) the order of each reactant: 1st order in A; zero order in B
  2. b) the order of the reaction: overall reaction is 1st ordered
  3. c) write the rate law: rate = k[A]
  4. d) calculate the rate constant, k: k = 1.75 x 10-2/s

3a. The decomposition of A2B3 is second order with a k = 6.5 x 10-5 M-1s -1 at 25oC.  If the initial concentration is 0.50 M, the concentration after 3 min is: 0.497 M

b. The half-life for the reaction in question 3a is: 3.08 x 104 s

4. The decomposition of AB is first order with a k = 2.3 x 10-7 s-1 at 45oC.  If the initial concentration is 0.25 M,  the concentration after 2.3 min is: 0.25 M

b. The half-life for the reaction in question 4a is: 3.01 x 106 s

5a. The concentration of reactant after 2.5 minutes if the inital concentration was 0.100 M and k = 6.93 x 10-3 s-1 for a first order reaction is: 0.0354 M

b. The half-life is: 100 s

6. For the first order reaction:

  \[SO_2Cl_2 \rightarrow SO_2  + Cl_2\]

 How long will it take to reach 0.31 x 10-3 M if the inital concentration was 1.25 x 10-3 M and k = 0.17/hr? 8.2 hrs

7. For the second order reaction  \(A \rightarrow B\) (k = 1.5 x 10-2/Ms),

  1.  if the initial concentration of A is 0.10M, the concentration of A after 4 min is: 0.074 M
  2.  the half-life is: 667 s