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Rate Law from Concentration versus Time Data The rate of the above reaction depe

ID: 999884 • Letter: R

Question

Rate Law from Concentration versus Time Data


The rate of the above reaction depends only on the concentration of nitrogen dioxide at temperatures below 225°C.  
At a temperature below 225°C the following data were obtained:

Time
(s)  

[NO2]
(mol/L)

0

0.800

1.85×103

0.669

4.62×103

0.537

6.94×103

0.462

1.39×104

0.325

2.78×104

0.204



(1) Which of the following expressions for the rate law (either differential or integrated) are completely consistent with the above experimental data.

Yes No  1/[NO2] = kt + 1/[NO2]0

Yes No  ln([NO2]/[NO2]0) = -kt

Yes No  d[NO]/dt = k[NO2]2

Yes No  k[NO2]2 = -d[CO]/dt

Yes No  k[NO2] = -d[NO2]/dt

(2) Calculate the rate constant (k).  Enter the numerical value and corresponding units.

NO2(g) + CO(g) NO(g) + CO2(g)

Explanation / Answer

!) rate law : ln ([NO2]/[NO2]0) = -kt i.e first order

2) plot of ln (NO2) vs t (neglecting the last two values) gives the following equation:

y = -78.882x-0.2403

here slope = k = 78.882 s-1