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Grade 11Physical Chemistry

ug is known to be ineffective after it has decomposed 25% the original concentration of a sample was 500 unkits/ml when analyzed 20 months later the concentration was found to be 450 units /ml assuming that decomposition is of 1st order what will be the expiry time of the drug?

Profile image of prasad
8 Years agoGrade 11
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1 Answer

Profile image of BIKRAM
8 Years ago
 
ln(A0/A)= Kt : K=(1/20×ln(500/450)=5.268×10-3 mon-1
A= 500-500×(25/100)=375 units/ml
expiry date (t)= (1/K)ln(500/375)= 54.6 month