Consider the hypothetical decomposition reaction: AB → A + B. The following data were collected at 423.15 K:
t (s)           [AB] (M)
0.0           2.500
20.0         2.099
40.0         1.762
60.0         1.479
80.0         1.241
100.0        1.042
Calculate the half-life of the reaction at the initial concentration.