Butadiene (C4H6) is an important compound for the industrial manufacturing of ru

Question

Butadiene (C4H6) is an important compound for the industrial manufacturing of rubber, however it is not indefinitely stable, especially at higher temperatures. The concentration of butadiene over time at 326oC is provided in chart form below. Use Excel or a similar graphing program to determine the order of the reaction, and then report the value for k.

time (s)      [butadiene] (M)

    0                0.0172

  900                0.0143

1800                0.0123

3600                0.00952

6000                0.00730

Explanation / Answer

For the zero order reaction,

Plot, butadiene concentration on y-axis vs. time on x-axis

slope = -[(final - initial)concentration/(final - initial) time] = constant

From the data,

Ist and IInd, slope = 3.2 x 10^-6

IInd and IIIrd, slope = 2.2 x 10^-6

IIIrd and IVth, slope = 1.5 x 10^-6

So slope is not constant, the reaction does not follow zero order kinetics

for first order reaction,

Plot, ln(butadiene) concentration on y-axis vs. time on x-axis

slope = -[ln(initial conc) - ln(final conc)]/(final - initial) time

from Ist and IInd, slope = 2.05 x 10^-4

from IInd and IIIrd, slope = 1.67 x 10^-4

from IIIrd and IVth, slope = 1.42 x 10^-4

So slope is not constant and thus reaction does not follow first order kinetics

for second order reaction,

Plot, 1/butadiene concentration on y-axis vs. time on x-axis

slope = [1/(final conc.) - 1/(initial conc.)]/(final - initial) time

from Ist and IInd, slope = 0.013

from IInd and IIIrd, slope = 0.013

from IIIrd and IVth, slope = 0.013

So slope is constant, that means the order of the reaction is 2nd order.

k = 0.013 M-1.s-1

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