Solve this:

​Q81. Out of 300g substance [ decomposes as per 1st order ], how much will remain after 18 hr ? (t_0.5 = 3 hr ) 

     1) 4.6 gm                         2) 5.6 gm                    3) 9.2 gm                   4) 6.4 gm


Q82. 75% of a first order process is completed in 30 min. The time required for 93.75% completion of same process (in hr) ?
              

        1) 1                                2) 120                          3) 2                            4) 0.25