In our kinetics lab we are plotting [tex] ln\frac{ A_{inf}-A }{ A_{inf} } [/tex] against -kt, i.e solving an pseudo first order reacting to find a rate constant. The problem however is finding out how the different errors (uncertainties) of the stuff in the ln term get translated to uncertainties in the y axis when i plot these.

I have tried using the error propagation rules to first solve for the numerator and then the entire paranthesis. The uncertainties is for A(inf)=0,008328 and A=0,05 and A(inf)=2,082 is just another constant so the only variable is A.

Trying to use the natural logarithm error propagation law then just causes chaos because my A is in the denominator which means that with higher Absorbance values for some reason my error gets larger and larger even though logically it should be the opposite since an error in 0,05 impacts A=0.1 more than A=2.0?