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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: pornstar on September 11, 2005, 03:48:22 AM

Title: First order kinetics
Post by: pornstar on September 11, 2005, 03:48:22 AM

hi all..this is my first post and here goes....

 what is the half-life of a compound if 75% of a given sample of the compound decomposes in 60min?assume first order kinetics..

 is the formula for this question 1/[A]t  =  kt  +  1/[A]0  ?  i dont know what to put as the questions didnt give enough info on the A.

Title: Re:First order kinetics
Post by: sdekivit on September 11, 2005, 04:25:32 AM

first order kinetics has the form of -d[A]/dt = k * [A]. Your formula is for second order kinetics.

then you can use the formula by solving this equation (or just look it up) and use the ratio [A](t) / [A](0) = 0,75 to find k. With k you can calculate the half life (formula can be found by taking [A](t) / [A](0) = 0,5)