Question

K.C. Berger has reported the following percentages of termination by combination in styrene polymerization.

t(°C): 30, 52, 62, 70, 80

% combination: 86, 80, 77, 68, 60

Evaluate the difference in activation energy between disproportionation and combination in the termination step.

Calculate the temperature at which the rates of combination and termination are equal.

Answer 1

A) According to the data, the termination by combination decreases with increasing temperature, increasing termination by disproportionation. In terms of activation energy we can conclude that the Ea for termination by combination increases with increasing temperature, and Ea decreases with increasing temperature in the case of the disproportionation, favoring this last one.

B) If plot %Combination vs temperature:

Using curve equation:

50%=-0,507T+104,02

(50-104,02)/-0,507=T

T=106,5 ^oC