Atomic mass of Potassium = Mass of 1 atom of Potassium = 39.1 amu Then Mass of 6.02 x 1023 atoms of potassium = 39.1 x 6.02 x 1023 amu = We already know that 1 mole = 6.02 x 1023 atoms Also Number of mole = mass in grams/ atomic mass Then Mass in gram = Number of mole x atomic mass = (39.1 x 6.02 x 1023)/(6.02 x 1023) = 39.1 g The correct option among all the options that are given in the question is the third option or option "B".
