# CHEMISTRY

NI 2

ENGR 1540 Worksheet 24 Chapter 11

1. The following experimental data were obtained for the reaction 2A+3B→C+2D

 [A] (mol L-1) [B] (mol L-1) Rate=Δ[C]/Δt (mol L-1 s-1) 0.127 0.15 0.033 0.127 0.30 0.132 0.255 0.15 0.066

Determine the reaction order for each reactant and the value of the constant.

2. The following experimental data were obtained for the reaction of NH4+ and NO2- in acidic solution. NH4+(aq)+NO2-(aq)→N2(g)+2H2O(l)

 [NH4+] (mol L-1) [NO2-] (mol L-1) Rate=Δ[N2]/Δt (mol L-1 s-1) 0.0092 0.098 3.33×10-7 0.0092 0.049 1.66×10-7 0.0488 0.196 3.51×10-6 0.0249 0.196 1.80×10-6

Determine the rate law for this reaction and calculate the rate constant.

3. Rate data were obtained at 25℃ for the following reaction. What is the rate law expression for this reaction? A+2B→C+2D

 Expt. Initial [A] (mol L-1) Initial [B] (mol L-1) Initial Rate of Formation of C (mol L-1 min-1) 1 0.10 0.10 3.0×10-4 2 0.30 0.30 9.0×10-4 3 0.10 0.30 3.0×10-4 4 0.20 0.40 6.0×10-4

4. For the reaction 2NO(g)+2H2(g)→N2(g)+2H2O(g) at 1100℃, the following data have been obtained:

 [NO] (mol L-1) [H2] (mol L-1) Rate=Δ[N2]/Δt (mol L-1 s-1) 5.0×10-3 0.32 0.012 1.0×10-2 0.32 0.048 1.0×10-2 0.64 0.096

Derive a rate law for the reaction and determine the value of the rate constant.

5. The reaction NO(g)+O2(g)→NO2(g)+O(g) plays a role in the formation of nitrogen dioxide in automobile engines. Suppose that a series of experiments measured the rate of this reaction at 500 K and produced the following data:

 [NO] (mol L-1) [O2] (mol L-1) Rate=-Δ[NO]/Δt (mol L-1 s-1) 0.002 0.005 8.0×10-17 0.002 0.010 1.6×10-16 0.006 0.005 2.4×10-16

Derive a rate law for the reaction and determine the value of the rate constant.

6. The decomposition of N2O5 in solution in carbon tetrachloride is a first-order reaction: 2N2O5→4NO2+O2 The rate constant at a given temperature is found to be 5.25×10-4 s-1. If the initial concentration of N2O5 is 0.200 M, what is its concentration after exactly 10 minutes have passed?

7. In the last problem, if the initial concentration of N2O5 is 0.100 M, how long will it take for the concentration to drop to 0.0100 times its original value?

8. For a drug to be effective in treating an illness, its levels in the bloodstream must be maintained for a period of time. One way to measure the level of a drug in the body is to measure its rate if appearance in the urine. The rate of excretion of penicillin is first order, with a half-life of about 30 min. If a person receives an injection of 25 mg of penicillin at t=0, how much penicillin remains in the body after 3 hours?

9. As with any drug, aspirin (acetylsalicylic acid) must remain in the bloodstream long enough to be effective. Assume that the removal of aspirin from the bloodstream into the urine is a first-order reaction, with a half-life of about 3 hours. The instructions on an aspirin bottle say to take 1 or 2 tablets every 4 hours. If a person takes 2 aspirin tablets, how much aspirin remains in the bloodstream when it is time for the second dose? (A standard tablet contains 325 mg of aspirin.)

10. A possible reaction for the degradation of the pesticide DDT to a less harmful compound was simulated in the laboratory. The reaction was found to be first order, with k=4.0×10-8 s-1 at 25℃. What is the half-life for the degradation of DDT in this experiment, in years?

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