The equilibrium constant, K, of a certain first order reaction was measured at t

Question

The equilibrium constant, K, of a certain first order reaction was measured at two temperatures, T. The data is shown in this table....

Map The equilibrium constant, K, of a certain first If you were going to graphically determine the enthalpy, order reaction was measured at two AH for this reaction, what points would you plot? temperatures, The data is shown in this table. Number Number To avoid rounding 0 errors, use three point 1 T (K) K significant figures in 275 3.81 the x values and four significant figures in 825 638 Number Number the y values. point 2: Determine the rise, run, and slope of the line formed by these points. slope rise run Number Number What is the standard enthalpy of this reaction? Number J mol AH

Explanation / Answer

We need to plot lnK on y axis and 1/T on x axis
K = 3.81
ln K = ln (3.81) = 1.3376
T = 275 K
1/T = 1/275 = 0.003636

point 1 is:
x = 0.003636
y = 1.3376

K = 6.38
ln K = ln (0.763) = 1.8532
T = 825 K
1/T = 1/725 = 0.001212

point 2 is:
x = 0.001212
y = 1.8532
----------------------------------------------------------------------------
rise = (y1-y2) = (1.3376 - 1.8532 ) = -0.5156
run = (x1-x2) = (0.003636 - 0.001212) = 0.002424

slope = rise/run
= -0.5156/0.002424
= - 212.706
-----------------------------------------------------------------------------
use:
slope = - delta Ho/R
-212.706 = - delta Ho / 8.314
delta Ho = 1768.4 J/mol

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