Question

2. The rate constants for the reaction CHCI3 (g)+CI (g) CHCI2 (g)+Cl2 (g) at different temperatures are tabulated below k (107 M1 s1) T (K) 357 400 1.72 2.53 3.82 458 5.20 524 5.61 7.65 533 615 a. Construct an Arrhenius plot of the tabulated data as presented above b. From the plot, calculate the values of the Arrhenius parameters A and Ea for the reaction.

Answer 1

Answer:

Given reaction is

CHCl2(g) + Cl2(g) -------> CHCl3(g) + Cl(g)

(a) The Arrhenius equation is

k=Ae^(-Ea/RT)

Where k=rate constant, Ea=activation energy, A= Pre-exponential factor, R=gas constant=8.314 J/mol.K, T=temperature.

(or) lnk=(-Ea/R)(1/T) + lnA

y=mx + b

Here y-axis is lnk and the x-axis is (1/T). Then slope is equall to m= -Ea/R and y-intercept, b=lnA.

The values are shown in below table

T(K)	k(M-1s-1)	1/T(K-1)	lnk
357	1.72E+07	0.002801	16.66042
400	2.53E+07	0.0025	17.04631
458	3.82E+07	0.002183	17.45835
524	5.20E+07	0.001908	17.76675
533	5.61E+07	0.001876	17.84265
615	7.65E+07	0.001626	18.1528

The Arrhenius plot, lnk vs 1/T is

y = a + b*x No Weighting 9.59383E-4 Equation Weight Residual Sum of Squares Pearson's r Adj. R-Square -0.99969 0.99921 Value Intercept 20.20335 Slope -1263.48773 Standard Error 0.03463 15.84363 Ink 0.0016 0.0018 0.0020 0.0022 0.0024 0.0026 0.0028 1/T

(b) From the plot, slope=-Ea/R=-1263.4877 K

Ea=1263.4877 K x 8.314 J/mol. K

Ea=10504.6 J/mol

(or) Ea ~ 10.505 kJ/mol. (Since 1kJ=1000 J)

and y-intercept=lnA=20.20335

A=e^20.20335=5.946 x 10⁸ M^-1 s^-1.

A=5.946 x 10⁸ M^-1 s^-1.

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