If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately. (AIPMT 2007)

For a first order reaction 10 2.303log a k t a x when t = 60 and x = 60% 2.303 100 2.303 100 log log 0.0153 60 100 60 60 40 k Now, 1/2 2.303 100 2.303 log log2 0.0153 100 50 0.0153 t x 2.303 0.3010 45.31min. 0.0153 x