For a first order reaction a graph is plotted between logaa−x(y-axis)  vs time in minutes(x-axis). If the slope of the graph is 0.1 then the half life of the reaction will be

K = 2.303tlogaa−x logaa-x = Kt2.303                         y=mx                    slope  = K2.303K2.303 = 0.1givenK = 0.2303 min−1t12  = 0.6930.2303minutest12  = 0.6930.2303×60seconds  =  180seconds