A reaction has a rate constant of 0.0396 sec-1; how long will it take (in minutes) until 0.292 mol/L of the compound is left, if there was 0.803 mol/L at the start? (give answer to 3 decimal places) ?

t = 0.426 min

Explanation:

assuming order one for the reaction:

- ra = k*Ca = - δCa/δt

∴ K = 0.0396/s

∴ Ca = 0.292 mol/L

∴ Cao = 0.803 mol/L

⇒ K∫δt = - ∫δCa/Ca

⇒ K*t = Ln (Cao/Ca)

⇒ t = [ Ln (Cao/Ca) ] / K

⇒ t = [ Ln (2.75) ] / (0.0396/s)

⇒ t = (1.0116) / (0.0396/s)

⇒ t = 25.545 s = 0.426 min