4 Fe + 3 O2 = 2 Fe2O3
M Fe2O3 = 160 g/mol
4 moli Fe.........160 g Fe2O3
3 moli Fe..................x
x = 120 g Fe2O3
n = m/M = 120/160 = 0,8 moli Fe2O3
2 K + O2 = 2 K2O
M K2O = 94 g/mol
2 moli K...........2*94 g K2O
m K2O = 188 g K2O
n = m/M = 188/94 = 2 moli K2O