  It is not common to consider the role of uncertainties in the rate
coefficients used in interstellar gas-phase chemical models. In this paper, we
report a new method to determine both the uncertainties in calculated molecular
abundances and their sensitivities to underlying uncertainties in the kinetic
data utilized. The method is used in hot core models to determine if previous
analyses of the age and the applicable cosmic-ray ionization rate are valid. We
conclude that for young hot cores ($\le 10^4$ yr), the modeling uncertainties
related to rate coefficients are reasonable so that comparisons with
observations make sense. On the contrary, the modeling of older hot cores is
characterized by strong uncertainties for some of the important species. In
both cases, it is crucial to take into account these uncertainties to draw
conclusions from the comparison of observations with chemical models.
