100% subst pura - 12% imp. = 88%
p% = puritatea = mp x 100 /mip
mp = p% x mip /100 = 190.09 x 88/100
=> mp = 167,28 g Fe pur
167,28... n moli....... a g
2Fe + 3Cl2 => 2FeCl3
2x56...... 3............2x162,5
=> n = 167,28x3x73/2x56
=> n = 4,48 moli Cl2
=> a = 167,28x2x162,5/2x56
=> a = 485,41 g FeCl3