Wavelength of Maximum Absorbance 592.30m Absorbance Data (include your units) ol
ID: 576066 • Letter: W
Question
Wavelength of Maximum Absorbance 592.30m Absorbance Data (include your units) old Time (s) 0 30 +-0.364 60 Absorbance 0.39 0.50 Absorbance Absorbance 120 150 180 210 240 270 300 O.223 3 0.144 0.34 o.2q 0.253 0.222 0.05S initial = ima' = 20,8 average T = average T 30 C Data Analysis 1. Your goal is to find the reaction order and rate constant from integrated rate law plots Using Excel or another spreadsheet program and the data above, calculate the natural log (In) of the absorbance and the inverse (or reciprocal) of the absorbance. Then construct a zeroth, first and second order plot using the room temperature data. Attach these fully labeled plots to your report. Which of these three is most linear? This plot gives you the reaction order The overall reaction order is Construct the integrated rate law plot for the "cold and "hot temperature reactions based on the order you just determined. (You may need to calculate the natural log or the inverse of the absorbances to do this.) Fit the data from all three of these plots (this includes the room temperature plot) to a straight line. Show the fitted equation of this line on your plot. Determine the slope of the best-fit line for each temperature. The slope provides the value for the rate constant. Report the rate constant (with units) below. n (k) average average T (K) rate constant (k) T (°C) 302303KExplanation / Answer
the relation between rate (-dCA/dt) and order (n) is given by
-dCA/dt= K CAn (1) where n is the order of reaction and K is the rate constant.
n=0, 1 and 2 gives rise to zero order , 1st order and 2nd order reactions. With the boundary conditions at t=0, CA= CAO and at t=t, CA=CA
when n=0, Eq.1 becomes, CA=CAO-Kt the plot of CA vs t has to be straight line with slope of -K.
when n=1, eq.1 beomces lnCA= lnCAO-Kt, the plot of ln CA vs t has to be straight line with slope of -K.
when n=2, eq.1 becomes 1/CA= 1/CAO+Kt, the plot of 1/CA vs t has to be straight line with slope of K.
in the data given, concentration is measued in terms of absorbance.
from the plots, it can be seen that the reaction is 1st order since the plot of ln( absorbance ) vs time is straight line while the plot of absorbance vs time is not straight line for satisfying zero order and also 1/absorbance vs time is also not straight line for satisfying second order.
hence the reaction is 1st oder.
Temperature (deg.c) Temperature, T ( K) ( t+273) 1/ T K ( rate constant) lnK
21.75 deg.c ( 21.77+273)= 294.75 K 1/294.75= 0.00339 0.007/sec -4.96
16.15 16.15+273= 289.15 K 1/289.15= 0.00345 0.004/sec -5.52
30 30+273= 303 K 1/303= 0.0033 0.009/sec -4.71
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