Question

for a first reaction the time required for completion of 30 % reaction is 20 min then what time will it take to complete 60% of the reaction

Answer 1

40 Minutes I think ..............

Answer 2

For first reaction is 30% completed,
so, x = 30, t  = 20 min .
so,
20 = 2.303 / K(log 100 / 100 - 30)
K = 2.303 / 20(log 100 / 70)
K = 2.303 / 20(log 0.020)
K = 2.303 / 20(1.698)
K = 0.11515(1.698)
K = 0.1955247
now reaction is 60% completed 
T = 2.303 / k(log a / a-x )
T = 2.303 / 0.19552(log 100 / 100 - 60)
T = 2.303 / 0.19552((log 100 / 40)
T = 2.303 / 0.19552(log 2.25 )
T = 11.778563(0.3979)
T = 46.87 min