dianacflores9856 dianacflores9856 23-12-2022 Physics Answered Natural rubidium has the average mass 85. 4678 amu and is composed of isotopes rb-85 (mass = 84. 9117 amu) and rb-87. The ratio of atoms rb-85/rb-87 in natural rubidium is 2. 591. Calculate the mass of rb-87.