PM Mn2O3 =157.88

100mg=0.1g
1/10 g./157.88 g/mole= 0.636*10^-3 moli
1 mole:6.02*10^23 molecole = 0.636*10^-3 moli : x molecole
x molecole= 5.98*10^17

moli di Mn= 2*0.036 *10^-3
Moli di O= 3*0.063*10^-3

1mole (Mn2O3) : 6.02*10^23= x: 2*10^19
X= 2*10^19/6.02*10^23=3.32*10^-5 moli

moli di Mn= 2*3.32*10^-5
Moli di O = 3*3.32 *10^-5