A first order reaction takes 40 min for 30% decomposition. Calculate t1/2.


Given:


Time t = 40 min


When 30% decomposition is undergone, 70% is the concentration.


We know, time taken


Where, k- rate constant


[R]° -Initial concentration


[R]-Concentration at time ‘t’





258.23 = (2.303/k)


We know, Half-life t1/2 = 0.693/k


Which can be written as, t1/2 = 0.3010 × (2.303/k)


t1/2 = 0.3010 × 258.23


t1/2 = 77.72 min


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